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Hematopoietic stem-cell transplantation (HSCT) is the transplantation of
multipotent hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within ...
s, usually derived from bone marrow,
peripheral blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
, or
umbilical cord blood Cord blood (umbilical cord blood) is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is collected because it contains stem cells, which can be used to treat hematopoietic and genetic disorders su ...
in order to replicate inside of a patient and to produce additional normal blood cells. It may be
autologous Autotransplantation is the transplantation of organs, tissues, or even particular proteins from one part of the body to another in the same person ('' auto-'' meaning "self" in Greek). The autologous tissue (also called autogenous, autogenei ...
(the patient's own stem cells are used),
allogeneic Allotransplant (''allo-'' meaning "other" in Greek) is the transplantation of cells, tissues, or organs to a recipient from a genetically non-identical donor of the same species. The transplant is called an allograft, allogeneic transplant, o ...
(the stem cells come from a donor) or syngeneic (from an
identical twin Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two ...
). It is most often performed for patients with certain
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
s of the
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
or bone marrow, such as multiple myeloma or
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
. In these cases, the recipient's immune system is usually destroyed with radiation or
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
before the transplantation. Infection and graft-versus-host disease are major complications of allogeneic HSCT. HSCT remains a dangerous procedure with many possible complications; it is reserved for patients with life-threatening diseases. As survival following the procedure has increased, its use has expanded beyond cancer to autoimmune diseases and hereditary
skeletal dysplasia Osteochondrodysplasia is a general term for a disorder of the development (dysplasia) of bone ("osteo") and cartilage ("chondro"). Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia. Non ...
s, notably
malignant infantile osteopetrosis Malignant infantile osteopetrosis is a rare osteosclerosing type of skeletal dysplasia that typically presents in infancy and is characterized by a unique radiographic appearance of generalized hyperostosis (excessive growth of bone). The genera ...
and mucopolysaccharidosis.


Medical uses


Indications

Indications for stem-cell transplantation are:


Malignant (cancerous)

*
Acute myeloid leukemia Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cell production. Symptoms may inclu ...
*
Chronic myeloid leukemia Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumulati ...
* Acute lymphoblastic leukemia *
Hodgkin lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated Reed–Sternberg cells (RS cells) are present in the patient's lymph nodes. The condition w ...
(relapsed, refractory) *
Non-Hodgkin lymphoma Non-Hodgkin lymphoma (NHL), also known as non-Hodgkin's lymphoma, is a group of blood cancers that includes all types of lymphomas except Hodgkin lymphomas. Symptoms include enlarged lymph nodes, fever, night sweats, weight loss, and tirednes ...
(relapsed, refractory) *
Neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the neck, chest, abdomen, or spine. Symptoms may include bone pain, a lump in th ...
*
Ewing sarcoma Ewing sarcoma is a type of cancer that forms in bone or soft tissue. Symptoms may include swelling and pain at the site of the tumor, fever, and a bone fracture. The most common areas where it begins are the legs, pelvis, and chest wall. In about ...
* Multiple myeloma *
Myelodysplastic syndrome A myelodysplastic syndrome (MDS) is one of a group of cancers in which immature blood cells in the bone marrow do not mature, and as a result, do not develop into healthy blood cells. Early on, no symptoms typically are seen. Later, symptoms may ...
s *
Glioma A glioma is a type of tumor that starts in the glial cells of the brain or the spine. Gliomas comprise about 30 percent of all brain tumors and central nervous system tumours, and 80 percent of all malignant brain tumours. Signs and symptoms ...
s, other
solid tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s


Nonmalignant (noncancerous)

* Thalassemia *
Sickle cell anemia Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red bl ...
* Aplastic anemia *
Fanconi anemia Fanconi anaemia (FA) is a rare genetic disease resulting in impaired response to DNA damage. Although it is a very rare disorder, study of this and other bone marrow failure syndromes has improved scientific understanding of the mechanisms of no ...
*
Malignant infantile osteopetrosis Malignant infantile osteopetrosis is a rare osteosclerosing type of skeletal dysplasia that typically presents in infancy and is characterized by a unique radiographic appearance of generalized hyperostosis (excessive growth of bone). The genera ...
* Mucopolysaccharidosis *
Paroxysmal nocturnal hemoglobinuria Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, life-threatening disease of the blood characterized by destruction of red blood cells by the complement system, a part of the body's innate immune system. This destructive process occu ...
*
Pyruvate kinase deficiency Pyruvate kinase deficiency is an inherited metabolic disorder of the enzyme pyruvate kinase which affects the survival of red blood cells. Both autosomal dominant and recessive inheritance have been observed with the disorder; classically, and ...
* Immune deficiency syndromes * Autoimmune diseases, including multiple sclerosis Many recipients of HSCTs are multiple myeloma or
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
patients who would not benefit from prolonged treatment with, or are already resistant to,
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
. Candidates for HSCTs include
pediatric Pediatrics ( also spelled ''paediatrics'' or ''pædiatrics'') is the branch of medicine that involves the medical care of infants, children, adolescents, and young adults. In the United Kingdom, paediatrics covers many of their youth until the ...
cases where the patient has an inborn defect such as
severe combined immunodeficiency Severe combined immunodeficiency (SCID), also known as Swiss-type agammaglobulinemia, is a rare genetic disorder characterized by the disturbed development of functional T cells and B cells caused by numerous genetic mutations that result in diffe ...
or congenital neutropenia with defective stem cells, and also children or adults with aplastic anemia who have lost their stem cells after birth. Other conditions treated with stem cell transplants include
sickle-cell disease Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blo ...
,
myelodysplastic syndrome A myelodysplastic syndrome (MDS) is one of a group of cancers in which immature blood cells in the bone marrow do not mature, and as a result, do not develop into healthy blood cells. Early on, no symptoms typically are seen. Later, symptoms may ...
,
neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the neck, chest, abdomen, or spine. Symptoms may include bone pain, a lump in th ...
,
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
,
Ewing's sarcoma Ewing sarcoma is a type of cancer that forms in bone or soft tissue. Symptoms may include swelling and pain at the site of the tumor, fever, and a bone fracture. The most common areas where it begins are the legs, pelvis, and chest wall. In about ...
,
desmoplastic small round cell tumor Desmoplastic small-round-cell tumor (DSRCT) is an aggressive and rare cancer that primarily occurs as masses in the abdomen. Other areas affected may include the lymph nodes, the lining of the abdomen, diaphragm, spleen, liver, chest wall, skull, ...
,
chronic granulomatous disease Chronic granulomatous disease (CGD), also known as Bridges–Good syndrome, chronic granulomatous disorder, and Quie syndrome, is a diverse group of hereditary diseases in which certain cells of the immune system have difficulty forming the reacti ...
, Hodgkin's disease and
Wiskott–Aldrich syndrome Wiskott–Aldrich syndrome (WAS) is a rare X-linked recessive disease characterized by eczema, thrombocytopenia (low platelet count), immune deficiency, and bloody diarrhea (secondary to the thrombocytopenia). It is also sometimes called the eczem ...
. More recently non-myeloablative, so-called mini transplant (microtransplantation) procedures, have been developed that require smaller doses of preparative chemotherapy and
radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...
. This has allowed HSCT to be conducted in the elderly and other patients who would otherwise be considered too weak to withstand a conventional treatment regimen.


Number of procedures

In 2006, 50,417 first HSCTs were recorded worldwide, according to a global survey of 1,327 centers in 71 countries conducted by the Worldwide Network for Blood and Marrow Transplantation. Of these, 28,901 (57%) were autologous and 21,516 (43%) were allogeneic (11,928 from family donors and 9,588 from unrelated donors). The main indications for transplant were lymphoproliferative disorders (55%) and leukemias (34%), and many took place in either Europe (48%) or the Americas (36%). The Worldwide Network for Blood and Marrow Transplantation reported the millionth transplant to have been undertaken in December 2012. In 2014, according to the World Marrow Donor Association, stem-cell products provided for unrelated transplantation worldwide had increased to 20,604 (4,149 bone-marrow donations, 12,506 peripheral blood stem-cell donations, and 3,949 cord-blood units).


Graft types


Autologous

Autologous HSCT requires the extraction (
apheresis Apheresis ( ἀφαίρεσις (''aphairesis'', "a taking away")) is a medical technology in which the blood of a person is passed through an apparatus that separates out one particular constituent and returns the remainder to the circulation ...
) of hematopoietic stem cells (HSCs) from the patient and storage of the harvested cells in a freezer. The patient is then treated with high-dose
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
with or without radiotherapy with the intention of eradicating the patient's malignant cell population at the cost of partial or complete bone marrow ablation (destruction of patient's bone marrow's ability to grow new blood cells). The patient's own stored stem cells are then transfused into his/her bloodstream, where they replace destroyed tissue and resume the patient's normal blood-cell production. Autologous transplants have the advantage of lower risk of infection during the immune-compromised portion of the treatment, since the recovery of immune function is rapid. Also, the incidence of patients experiencing rejection is very rare (and graft-versus-host disease impossible) due to the donor and recipient being the same individual. These advantages have established autologous HSCT as one of the standard second-line treatments for such diseases as
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
. For other cancers such as
acute myeloid leukemia Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cell production. Symptoms may inclu ...
, though, the reduced mortality of the autogenous relative to allogeneic HSCT may be outweighed by an increased likelihood of cancer relapse and related mortality, so the allogeneic treatment may be preferred for those conditions. Researchers have conducted small studies using nonmyeloablative HSCT as a possible treatment for type I (insulin dependent) diabetes in children and adults. Results have been promising, but , speculating whether these experiments will lead to effective treatments for diabetes is premature.


Allogeneic

Allogeneic HSCT involves two people – the (healthy) donor and the (patient) recipient. Allogeneic HSC donors must have a tissue (
human leukocyte antigen The human leukocyte antigen (HLA) system or complex is a complex of genes on chromosome 6 in humans which encode cell-surface proteins responsible for the regulation of the immune system. The HLA system is also known as the human version of th ...
, HLA) type that matches the recipient. Matching is performed on the basis of variability at three or more loci of the HLA gene, and a perfect match at these loci is preferred. Even if a good match exists at these critical
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...
s, the recipient will require
immunosuppressive Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reacti ...
medications to mitigate graft-versus-host disease. Allogeneic transplant donors may be related (usually a closely HLA-matched sibling), syngeneic (a
monozygotic Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two ...
or identical twin of the patient – necessarily extremely rare since few patients have an identical twin, but offering a source of perfectly HLA-matched stem cells) or unrelated (donor who is not related and found to have very close degree of HLA matching). Unrelated donors may be found through a registry of bone-marrow donors, such as the
National Marrow Donor Program The National Marrow Donor Program (NMDP) is a nonprofit organization founded in 1986 and based in Minneapolis, Minnesota, that operates the Be The Match Registry of volunteer hematopoietic cell donors and umbilical cord blood units in the United ...
(NMDP) in the U.S. People who would like to be tested for a specific family member or friend without joining any of the bone-marrow registry data banks may contact a private HLA testing laboratory and be tested with a blood test or mouth swab to see if they are a potential match. A "
savior sibling A savior baby or savior sibling is a child who is conceived in order to provide a stem cell transplant to a sibling that is affected with a fatal disease, such as cancer or Fanconi anemia, that can best be treated by hematopoietic stem cell transp ...
" may be intentionally selected by
preimplantation genetic diagnosis Preimplantation genetic diagnosis (PGD or PIGD) is the genetic profiling of embryos prior to implantation (as a form of embryo profiling), and sometimes even of oocytes prior to fertilization. PGD is considered in a similar fashion to prenatal ...
to match a child both regarding HLA type and being free of any obvious inheritable disorder. Allogeneic transplants are also performed using umbilical
cord blood Cord blood (umbilical cord blood) is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is collected because it contains stem cells, which can be used to treat hematopoietic and genetic disorders s ...
as the source of stem cells. In general, by transfusing healthy stem cells to the recipient's bloodstream to reform a healthy immune system, allogeneic HSCTs appear to improve chances for cure or long-term remission once the immediate transplant-related complications are resolved. A compatible donor is found by doing additional HLA testing from the blood of potential donors. The HLA genes fall in two categories (types I and II). In general, mismatches of the type-I genes (i.e. ''
HLA-A HLA-A is a group of human leukocyte antigens (HLA) that are encoded by the HLA-A locus, which is located at human chromosome 6p21.3. HLA is a major histocompatibility complex (MHC) antigen specific to humans. HLA-A is one of three major types of ...
,
HLA-B HLA-B (major histocompatibility complex, class I, B) is a human gene that provides instructions for making a protein that plays a critical role in the immune system. HLA-B is part of a family of genes called the human leukocyte antigen (HLA) compl ...
'', or ''
HLA-C HLA-C belongs to the MHC (human = HLA) class I heavy chain receptors. The C receptor is a heterodimer consisting of a HLA-C mature gene product and β2-microglobulin. The mature C chain is anchored in the membrane. MHC Class I molecules, like HL ...
'') increase the risk of graft rejection. A mismatch of an HLA type II gene (i.e. ''
HLA-DR HLA-DR is an MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31. The complex of HLA-DR (Human Leukocyte Antigen – DR isotype) and peptide, generally between 9 and 30 amino acids in ...
'' or'' HLA-DQB1'') increases the risk of graft-versus-host disease. In addition, a genetic mismatch as small as a single DNA base pair is significant, so perfect matches require knowledge of the exact DNA sequence of these genes for both donor and recipient. Leading transplant centers currently perform testing for all five of these HLA genes before declaring that a donor and recipient are HLA-identical.
Race Race, RACE or "The Race" may refer to: * Race (biology), an informal taxonomic classification within a species, generally within a sub-species * Race (human categorization), classification of humans into groups based on physical traits, and/or s ...
and ethnicity are known to play a major role in donor recruitment drives, as members of the same ethnic group are more likely to have matching genes, including the genes for HLA. , at least two commercialized allogeneic cell therapies have been developed, Prochymal and Cartistem.


Sources and storage of cells

To limit the risks of transplanted stem-cell rejection or of severe graft-versus-host disease in allogeneic HSCT, the donor should preferably have the same HLA-typing as the recipient. About 25 to 30% of allogeneic HSCT recipients have an HLA-identical sibling. Even so-called "perfect matches" may have mismatched minor alleles that contribute to graft-versus-host disease.


Bone marrow

In the case of a bone-marrow transplant, the HSCs are removed from a large bone of the donor, typically the pelvis, through a large needle that reaches the center of the bone. The technique is referred to as a bone-marrow harvest and is performed under
local Local may refer to: Geography and transportation * Local (train), a train serving local traffic demand * Local, Missouri, a community in the United States * Local government, a form of public administration, usually the lowest tier of administrat ...
or
general anesthesia General anaesthesia (UK) or general anesthesia (US) is a medically induced loss of consciousness that renders the patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general ...
.


Peripheral blood stem cells

Peripheral blood stem cells are now the most common source of stem cells for HSCT. They are collected from the blood through a process known as
apheresis Apheresis ( ἀφαίρεσις (''aphairesis'', "a taking away")) is a medical technology in which the blood of a person is passed through an apparatus that separates out one particular constituent and returns the remainder to the circulation ...
. The donor's blood is withdrawn through a sterile needle in one arm and passed through a machine that removes
white blood cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...
. The red blood cells are returned to the donor. The peripheral stem cell yield is boosted with daily subcutaneous injections of granulocyte-colony stimulating factor, serving to mobilize stem cells from the donor's bone marrow into the peripheral circulation.


Amniotic fluid

Extracting stem cells from amniotic fluid is possible for both
autologous Autotransplantation is the transplantation of organs, tissues, or even particular proteins from one part of the body to another in the same person ('' auto-'' meaning "self" in Greek). The autologous tissue (also called autogenous, autogenei ...
and
heterologous The term heterologous has several meanings in biology. Gene expression In cell biology and protein biochemistry, heterologous expression means that a protein is experimentally put into a cell that does not normally make (i.e., express) that ...
uses at the time of childbirth.


Umbilical cord blood

Umbilical cord blood is obtained when a mother donates her infant's
umbilical cord In placental mammals, the umbilical cord (also called the navel string, birth cord or ''funiculus umbilicalis'') is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord is physiologi ...
and
placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...
after birth. Cord blood has a higher concentration of HSCs than is normally found in adult blood, but the small quantity of blood obtained from an umbilical cord (typically about 50 ml) makes it more suitable for transplantation into small children than into adults. Newer techniques using ''ex vivo'' expansion of cord blood units or the use of two cord blood units from different donors allow cord blood transplants to be used in adults. Cord blood can be harvested from the umbilical cord of a child being born after
preimplantation genetic diagnosis Preimplantation genetic diagnosis (PGD or PIGD) is the genetic profiling of embryos prior to implantation (as a form of embryo profiling), and sometimes even of oocytes prior to fertilization. PGD is considered in a similar fashion to prenatal ...
for HLA matching (see
PGD for HLA matching A savior baby or savior sibling is a child who is conceived in order to provide a stem cell transplant to a sibling that is affected with a fatal disease, such as cancer or Fanconi anemia, that can best be treated by hematopoietic stem cell trans ...
) to donate to an ill sibling requiring HSCT.


Storage of HSC

Unlike other organs, bone-marrow cells can be frozen (
cryopreserved Cryo-preservation or cryo-conservation is a process where organisms, organelles, cells, tissues, extracellular matrix, organs, or any other biological constructs susceptible to damage caused by unregulated chemical kinetics are preserved by co ...
) for prolonged periods without damaging too many cells. This is a necessity with autologous HSCs because the cells must be harvested from the recipient months in advance of the transplant treatment. In the case of allogeneic transplants, fresh HSCs are preferred to avoid cell loss that might occur during the freezing and thawing process. Allogeneic cord blood is stored frozen at a cord blood bank because it is only obtainable at the time of
childbirth Childbirth, also known as labour and delivery, is the ending of pregnancy where one or more babies exits the internal environment of the mother via vaginal delivery or caesarean section. In 2019, there were about 140.11 million births glob ...
. To cryopreserve HSCs, a preservative, dimethyl sulfoxide, must be added, and the cells must be cooled very slowly in a controlled-rate freezer to prevent
osmotic Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region o ...
cellular injury during ice-crystal formation. HSCs may be stored for years in a cryofreezer, which typically uses liquid nitrogen.


Conditioning regimens


Myeloablative

The chemotherapy or irradiation given immediately prior to a transplant is called the conditioning regimen, the purpose of which is to help eradicate the patient's disease prior to the infusion of HSCs and to suppress immune reactions. The bone marrow can be ablated (destroyed) with dose-levels that cause minimal injury to other tissues. In allogeneic transplants, a combination of cyclophosphamide with total body irradiation is conventionally employed. This treatment also has an
immunosuppressive Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reacti ...
effect that prevents rejection of the HSCs by the recipient's
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...
. The post-transplant prognosis often includes acute and chronic graft-versus-host disease that may be life-threatening. In certain leukemias, though, this can coincide with protection against cancer relapse owing to the
graft-versus-tumor effect Graft-versus-tumor effect (GvT) appears after allogeneic hematopoietic stem cell transplantation (HSCT). The graft contains donor T cells (T lymphocytes) that can be beneficial for the recipient by eliminating residual malignant cells. GvT might d ...
. Autologous transplants may also use similar conditioning regimens, but many other chemotherapy combinations can be used depending on the type of disease.


Nonmyeloablative

A newer treatment approach, nonmyeloablative allogeneic transplantation, also termed reduced-intensity conditioning (RIC), uses doses of chemotherapy and radiation too low to eradicate all the bone-marrow cells of the recipient. Instead, nonmyeloablative transplants run lower risks of serious infections and transplant-related mortality while relying upon the graft versus tumor effect to resist the inherent increased risk of cancer relapse. Also significantly, while requiring high doses of immunosuppressive agents in the early stages of treatment, these doses are less than for conventional transplants. This leads to a state of mixed
chimerism A genetic chimerism or chimera ( ) is a single organism composed of cells with more than one distinct genotype. In animals, this means an individual derived from two or more zygotes, which can include possessing blood cells of different blood ...
early after transplant where both recipient and donor HSC coexist in the bone marrow space. Decreasing doses of immunosuppressive therapy then allow donor
T-cell A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell r ...
s to eradicate the remaining recipient HSCs and to induce the graft-versus-tumor effect. This effect is often accompanied by mild graft-versus-host disease, the appearance of which is often a surrogate marker for the emergence of the desirable graft versus tumor effect, and also serves as a signal to establish an appropriate dosage level for sustained treatment with low levels of immunosuppressive agents. Because of their gentler conditioning regimens, these transplants are associated with a lower risk of transplant-related mortality, so allow patients who are considered too high-risk for conventional allogeneic HSCT to undergo potentially curative therapy for their disease. The optimal conditioning strategy for each disease and recipient has not been fully established, but RIC can be used in elderly patients unfit for myeloablative regimens, for whom a higher risk of cancer relapse may be acceptable.


Engraftment

After several weeks of growth in the bone marrow, expansion of HSCs and their progeny is sufficient to normalize the blood cell counts and reinitiate the immune system. The offspring of donor-derived HSCs have been documented to populate many different organs of the recipient, including the
heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
,
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
, and muscle, and these cells had been suggested to have the abilities of regenerating injured tissue in these organs. However, recent research has shown that such lineage infidelity does not occur as a normal phenomenon.
Chimerism A genetic chimerism or chimera ( ) is a single organism composed of cells with more than one distinct genotype. In animals, this means an individual derived from two or more zygotes, which can include possessing blood cells of different blood ...
monitoring is a method to monitor the balance between the patient's own stem cells and the new stem cells from a donor. In cases where the patient's own stem cells are increasing in number after treatment, the treatment may potentially not have worked as intended.


Complications

HSCT is associated with a high treatment-related mortality in the recipient, which limits its use to conditions that are themselves life-threatening. (The one-year survival rate has been estimated to be roughly 60%, although this figure includes deaths from the underlying disease, as well as from the transplant procedure.) Major complications include
veno-occlusive disease Hepatic veno-occlusive disease (VOD) or veno-occlusive disease with immunodeficiency is a potentially life-threatening condition in which some of the small veins in the liver are obstructed. It is a complication of high-dose chemotherapy given bef ...
,
mucositis Mucositis is the painful inflammation and ulceration of the mucous membranes lining the digestive tract, usually as an adverse effect of chemotherapy and radiotherapy treatment for cancer. Mucositis can occur anywhere along the gastrointestina ...
, infections (
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
), graft-versus-host disease, and the development of new
malignancies Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...
.


Infection

Bone-marrow transplantation usually requires that the recipient's own bone marrow be destroyed (myeloablation). Prior to the administration of new cells (engraftment), patients may go for several weeks without appreciable numbers of white blood cells to help fight
infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...
. This puts a patient at high risk of infections, sepsis, and septic shock, despite
prophylactic Preventive healthcare, or prophylaxis, consists of measures taken for the purposes of disease prevention.Hugh R. Leavell and E. Gurney Clark as "the science and art of preventing disease, prolonging life, and promoting physical and mental hea ...
antibiotics. However,
antiviral Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do no ...
medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and ...
s, such as
acyclovir Aciclovir (ACV), also known as acyclovir, is an antiviral medication. It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Other uses include prevention of cytomegalovirus infections following t ...
and
valacyclovir Valaciclovir, also spelled valacyclovir, is an antiviral medication used to treat outbreaks of herpes simplex or herpes zoster (shingles). It is also used to prevent cytomegalovirus following a kidney transplant in high risk cases. It is taken ...
, are quite effective in prevention of HSCT-related outbreak of herpetic infection in
seropositive Serostatus refers to the presence or absence of a serological marker in the blood. The presence of detectable levels of a specific marker within the serum is considered seropositivity, while the absence of such levels is considered seronegativity. ...
patients. The immunosuppressive agents employed in allogeneic transplants for the prevention or treatment of graft-versus-host disease further increase the risk of opportunistic infection. Immunosuppressive drugs are given for a minimum of six months after a transplantation, or much longer if required for the treatment of graft-versus-host disease. Transplant patients lose their acquired immunity, for example immunity to childhood diseases such as measles or
polio Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe s ...
. So, transplant patients must be retreated with childhood
vaccines A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified.< ...
once they are off immunosuppressive medications.


Veno-occlusive disease

Severe liver injury can result from hepatic veno-occlusive disease (VOD), newly termed sinusoidal obstruction syndrome (SOS). Elevated levels of bilirubin,
hepatomegaly Hepatomegaly is the condition of having an enlarged liver. It is a non-specific medical sign having many causes, which can broadly be broken down into infection, hepatic tumours, or metabolic disorder. Often, hepatomegaly will present as an abdo ...
, and fluid retention are clinical hallmarks of this condition. The appreciation of the generalized cellular injury and obstruction in
hepatic vein In human anatomy, the hepatic veins are the veins that drain venous blood from the liver into the inferior vena cava (as opposed to the hepatic portal vein which conveys blood from the gastrointestinal organs to the liver). There are usually thre ...
sinuses is now greater. Severe cases of SOS are associated with a high mortality rate. Anticoagulants or
defibrotide Defibrotide, sold under the brandname Defitelio, is a mixture of single-stranded oligonucleotides that is purified from the intestinal mucosa of pigs. It is used to treat veno-occlusive disease of the liver of people having had a bone marrow tran ...
may be effective in reducing the severity of VOD but may also increase bleeding complications. Ursodiol has been shown to help prevent VOD, presumably by facilitating the flow of bile.


Mucositis

The injury of the mucosal lining of the mouth and throat is a common regimen-related toxicity following ablative HSCT regimens. It is usually not life-threatening, but is very painful, and prevents eating and drinking. Mucositis is treated with pain medications plus intravenous infusions to prevent dehydration and malnutrition.


Hemorrhagic cystitis

The mucosal lining of the bladder is affected in about 5% of children undergoing HSCT. This causes
hematuria Hematuria or haematuria is defined as the presence of blood or red blood cells in the urine. “Gross hematuria” occurs when urine appears red, brown, or tea-colored due to the presence of blood. Hematuria may also be subtle and only detectable w ...
(blood in urine), frequent urination, abdominal pain and
thrombocytopenia Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients a ...
.


Graft-versus-host disease

Graft-versus-host disease (GvHD) is an inflammatory disease that is unique to allogeneic transplantation. It is an attack by the "new" bone marrow's immune cells against the recipient's tissues. This can occur even if the donor and recipient are HLA-identical because the immune system can still recognize other differences between their tissues. It is aptly named graft-versus-host disease because bone-marrow transplantation is the only transplant procedure in which the transplanted cells must accept the body rather than the body accepting the new cells. Acute GvHD typically occurs in the first three months after transplantation and may involve the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...
, intestine, or
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
. High-dose corticosteroids, such as
prednisone Prednisone is a glucocorticoid medication mostly used to suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium due to cancer and ad ...
, are a standard treatment, but this immunosuppressive treatment often leads to deadly infections. Chronic GvHD may also develop after allogeneic transplant. It is the major source of late treatment-related complications, although it less often results in death. In addition to inflammation, chronic GvHD may lead to the development of
fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...
, or scar tissue, similar to
scleroderma Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas ...
; it may cause functional disability and require prolonged immunosuppressive therapy. GvHD is usually mediated by T cells, which react to foreign peptides presented on the major histocompatibility complex of the host. Further research is needed to determine whether mesenchymal stromal cells can be use for prophylaxis and treatment of GvHD.


Graft-versus-tumor effect

Graft-versus-tumor effect (GVT), or "graft versus leukemia" effect, is the beneficial aspect of the GvHD phenomenon. For example, HSCT patients with either acute, or in particular chronic, GvHD after an allogeneic transplant tend to have a lower risk of cancer relapse. This is due to a therapeutic immune reaction of the grafted donor T lymphocytes against the diseased bone marrow of the recipient. This lower rate of relapse accounts for the increased success rate of allogeneic transplants, compared to transplants from identical twins, and indicates that allogeneic HSCT is a form of immunotherapy. GVT is the major benefit of transplants that do not employ the highest immunosuppressive regimens. Graft versus tumor is mainly beneficial in diseases with slow progress, e.g. chronic leukemia, low-grade lymphoma, and in some cases multiple myeloma, but is less effective in rapidly growing acute leukemias.Memorial Sloan-Kettering Cancer Center > Blood & Marrow Stem Cell Transplantation > The Graft-versus-Tumor Effect
Last Updated: 20 Nov. 2003. Retrieved on 6 April 2009
If cancer relapses after HSCT, another transplant can be performed, infusing the patient with a greater quantity of donor white blood cells (
donor lymphocyte infusion Donor lymphocyte (''or leukocyte'') infusion (DLI) or buffy coat infusion is a form of adoptive immunotherapy used after hematopoietic stem cell transplantation. History Formerly, the only treatment option that offered relapsed bone marrow transp ...
).


Malignancies

Patients after HSCT are at a higher risk for
oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or or ...
carcinoma. Post-HSCT
oral cancer Oral cancer, also known as mouth cancer, is cancer of the lining of the lips, mouth, or upper throat. In the mouth, it most commonly starts as a painless white patch, that thickens, develops red patches, an ulcer, and continues to grow. When on ...
may have more aggressive behavior with poorer prognosis, when compared to oral cancer in non-HSCT patients. A meta-analysis showed that the risk of secondary cancers such as
bone cancer A bone tumor is an abnormal growth of tissue in bone, traditionally classified as noncancerous (benign) or cancerous (malignant). Cancerous bone tumors usually originate from a cancer in another part of the body such as from lung, breast, thy ...
,
head and neck cancers Head and neck cancer develops from tissues in the lip and oral cavity (mouth), larynx (throat), salivary glands, nose, sinuses or the skin of the face. The most common types of head and neck cancers occur in the lip, mouth, and larynx. Symptoms ...
, and melanoma, with standardized incidence ratios of 10.04 (3.48–16.61), 6.35 (4.76–7.93), and 3.52 (2.65–4.39), respectively, was significantly increased after HSCT. So, diagnostic tests for these cancers should be included in the screening program of these patients for the prevention and early detection of these cancers.


Prognosis

Prognosis in HSCT varies widely dependent upon disease type, stage, stem-cell source, HLA-matched status (for allogeneic HSCT), and conditioning regimen. A transplant offers a chance for cure or long-term remission if the inherent complications of graft versus host disease, immunosuppressive treatments and the spectrum of opportunistic infections can be survived. In recent years, survival rates have been gradually improving across almost all populations and subpopulations receiving transplants. Mortality for allogeneic stem cell transplantation can be estimated using the prediction model created by Sorror ''et al''., using the Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI). The HCT-CI was derived and validated by investigators at the
Fred Hutchinson Cancer Research Center The Fred Hutchinson Cancer Center, formerly known as the Fred Hutchinson Cancer Research Center and also known as Fred Hutch or The Hutch, is a cancer research institute established in 1975 in Seattle, Washington. History The center grew out o ...
in the U.S. The HCT-CI modifies and adds to a well-validated comorbidity index, the Charlson comorbidity index (CCI) (Charlson, ''et al''.) The CCI was previously applied to patients undergoing allogeneic HCT, but appears to provide less survival prediction and discrimination than the HCT-CI scoring system. Patients who were successfully treated with HSCT and total body irradiation in childhood were found to have increased fat mass percentage, leading to significantly decreased exercise capacity in adulthood. This suggests patients who underwent successful treatment with HSCT have an increased predisposition to cardiovascular disease later in life.


Risks to donor

The risks of a complication depend on patient characteristics, health care providers, and the apheresis procedure, and the colony-stimulating factor used (
G-CSF Granulocyte colony-stimulating factor (G-CSF or GCSF), also known as colony-stimulating factor 3 (CSF 3), is a glycoprotein that stimulates the bone marrow to produce granulocytes and stem cells and release them into the bloodstream. Functiona ...
). G-CSF drugs include
filgrastim Filgrastim, sold under the brand name Neupogen among others, is a medication used to treat low neutrophil count. Low neutrophil counts may occur with HIV/AIDS, following chemotherapy or radiation poisoning, or be of an unknown cause. It may ...
(Neupogen, Neulasta), and
lenograstim Lenograstim is a recombinant granulocyte colony-stimulating factor Granulocyte colony-stimulating factor (G-CSF or GCSF), also known as colony-stimulating factor 3 (CSF 3), is a glycoprotein that stimulates the bone marrow to produce granulocy ...
(Graslopin).


Drug risks

Filgrastim is typically dosed in the 10 microgram/kg level for 4–5 days during the harvesting of stem cells. The documented adverse effects of filgrastim include
splenic rupture A splenic injury, which includes a ruptured spleen, is any injury to the spleen. The rupture of a normal spleen can be caused by trauma, such as a traffic collision. Signs and symptoms In minor injuries with little bleeding, there may be abdomin ...
, acute respiratory distress syndrome, alveolar hemorrhage, and allergic reactions (usually experienced in first 30 minutes).Neupogen Prescription information
In addition, platelet and hemoglobin levels dip postprocedurally, not returning to normal until after a month. The question of whether geriatrics (patients over 65) react the same as patients under 65 has not been sufficiently examined. Coagulation issues and inflammation of atherosclerotic plaques are known to occur as a result of G-CSF injection. G-CSF has also been described to induce genetic changes in
agranulocyte In immunology, agranulocytes (also known as nongranulocytes or mononuclear leukocytes) are one of the two types of leukocytes (white blood cells), the other type being granulocytes. Agranular cells are noted by the absence of granules in their ...
s of normal donors. There is no statistically significant evidence either for or against the hypothesis that myelodysplasia (MDS) or acute myeloid leukaemia (AML) can be induced by G-CSF in susceptible individuals.


Access risks

Blood is drawn from a peripheral vein in a majority of patients, but a central line to the jugular, subclavian, and femoral veins may be used. Adverse reactions during apheresis were experienced in 20% of women and 8% of men, these adverse events primarily consisted of numbness/tingling, multiple line attempts, and nausea.


Clinical observations

A study involving 2,408 donors (aged 18–60 years) indicated that
bone pain Bone pain (also known medically by several other names) is pain coming from a bone, and is caused by damaging stimuli. It occurs as a result of a wide range of diseases or physical conditions or both, and may severely impair the quality of life. ...
(primarily back and hips) as a result of filgrastim treatment is observed in 80% of donors. Donation is not recommended for those with a history of back pain. Other symptoms observed in more than 40 percent of donors include muscle pain, headache, fatigue, and difficulty sleeping. These symptoms all returned to baseline 1 month after donation in the majority of patients. In one meta-study that incorporated data from 377 donors, 44% of patients reported having adverse side effects after peripheral blood HSCT. Side effects included pain prior to the collection procedure as a result of G-CSF injections, and postprocedural generalized skeletal pain, fatigue, and reduced energy.


Severe reactions

A study that surveyed 2,408 donors found that serious adverse events (requiring prolonged hospitalization) occurred in 15 donors (at a rate of 0.6%), although none of these events was fatal. Donors were not observed to have higher than normal rates of cancer with up to 4–8 years of follow-up. One study based on a survey of medical teams covered about 24,000 peripheral blood HSCT cases between 1993 and 2005, and found a serious cardiovascular adverse reaction rate of about one in 1,500. This study reported a cardiovascular-related fatality risk within the first 30 days of HSCT of about two in 10,000.


History

In 1939, a woman with aplastic anaemia received the first human bone marrow transfusion. This patient received regular blood transfusions, and an attempt was made to increase her leukocyte and platelet counts by intravenous bone marrow injection without unexpected reaction. Stem-cell transplantation was pioneered using bone marrow-derived stem cells by a team at the
Fred Hutchinson Cancer Research Center The Fred Hutchinson Cancer Center, formerly known as the Fred Hutchinson Cancer Research Center and also known as Fred Hutch or The Hutch, is a cancer research institute established in 1975 in Seattle, Washington. History The center grew out o ...
from the 1950s through the 1970s led by E. Donnall Thomas, whose work was later recognized with a
Nobel Prize in Physiology or Medicine The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
. Thomas' work showed that bone-marrow cells infused intravenously could repopulate the bone marrow and produce new blood cells. His work also reduced the likelihood of developing a life-threatening graft-versus-host disease. Collaborating with
Eloise Giblett Eloise "Elo" R. Giblett (January 17, 1921 – September 16, 2009) was a pioneering genetic scientist and hematologist who discovered the first recognized immunodeficiency disease, adenosine deaminase deficiency. Giblett was a Professor of Medici ...
, a professor at the
University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattl ...
, he discovered genetic markers that could confirm donor matches. The first physician to perform a successful human bone-marrow transplant on a disease other than cancer was Robert A. Good at the
University of Minnesota The University of Minnesota, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public land-grant research university in the Twin Cities of Minneapolis and Saint Paul, Minnesota, United States. ...
in 1968. In 1975, John Kersey, also of the University of Minnesota, performed the first successful bone-marrow transplant to cure lymphoma. His patient, a 16-year-old-boy, is today the longest-living lymphoma transplant survivor.


Donor registration and recruitment

At the end of 2012, 20.2 million people had registered their willingness to be a bone-marrow donor with one of the 67 registries from 49 countries participating in Bone Marrow Donors Worldwide. Around 17.9 million of these registered donors had been ABDR typed, allowing easy matching. A further 561,000 cord blood units had been received by one of 46 cord blood banks from 30 countries participating. The highest total number of bone-marrow donors registered were those from the U.S. (8.0 million), and the highest number per capita were those from Cyprus (15.4% of the population). Within the U.S., racial minority groups are the least likely to be registered, so are the least likely to find a potentially life-saving match. In 1990, only six African Americans were able to find a bone-marrow match, and all six had common European genetic signatures. Africans are more genetically diverse than people of European descent, which means that more registrations are needed to find a match. Bone marrow and cord blood banks exist in
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
, and a new program is beginning in
Nigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
. Many people belonging to different races are requested to donate as a shortage of donors exists in African, mixed race, Latino, aboriginal, and many other communities. Two registries in the U.S. recruit unrelated allogeneic donors: NMDP or Be the Match, and the Gift of Life Marrow Registry.


Research


HIV

In 2007, a team of doctors in Berlin, Germany, including
Gero Hütter Gero Hütter (born 18 December 1968) is a German hematologist. Hütter and his medical team transplanted bone marrow deficient in a key HIV receptor to a leukemia patient, Timothy Ray Brown, who was also infected with human immunodeficiency virus ...
, performed a stem-cell transplant for
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
patient
Timothy Ray Brown Timothy Ray Brown (March 11, 1966September 29, 2020) was an American considered to be the first person cured of HIV/AIDS. Brown was called "The Berlin Patient" at the 2008 Conference on Retroviruses and Opportunistic Infections, where his cure ...
, who was also
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
-positive. From 60 matching donors, they selected a CR5Δ32 homozygous individual with two genetic copies of a rare variant of a
cell surface receptor Cell surface receptors (membrane receptors, transmembrane receptors) are receptors that are embedded in the plasma membrane of cells. They act in cell signaling by receiving (binding to) extracellular molecules. They are specialized integral m ...
. This genetic trait confers resistance to HIV infection by blocking attachment of HIV to the cell. Roughly one in 1,000 people of European ancestry have this inherited
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
, but it is rarer in other populations. The transplant was repeated a year later after a leukemia relapse. Over three years after the initial transplant, and despite discontinuing
antiretroviral therapy The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs as a strategy to control HIV infection. There are several classes of antiretroviral agents that act on different stages of the HIV life-cycle. The use of multi ...
, researchers cannot detect HIV in the transplant recipient's blood or in various biopsies of his tissues. Levels of HIV-specific antibodies have also declined, leading to speculation that the patient may have been functionally cured of HIV, but scientists emphasise that this is an unusual case. Potentially fatal transplant complications (the "Berlin patient" developed graft-versus-host disease and
leukoencephalopathy Leukoencephalopathy (leukodystrophy-like diseases) is a term that describes all of the brain white matter diseases, whether their molecular cause is known or unknown. It can refer specifically to any of these diseases: *Progressive multifocal leuko ...
) mean that the procedure could not be performed in others with HIV, even if sufficient numbers of suitable donors were found. In 2012,
Daniel Kuritzkes Daniel Robert Kuritzkes is an American physician. Kuritzkes studied molecular biophysics and biochemistry at Yale University and completed his medical degree at Harvard Medical School. He was trained in internal medicine and infectious diseases at ...
reported results of two stem-cell transplants in patients with HIV. They did not, however, use donors with the Δ32 deletion. After their transplant procedures, both were put on antiretroviral therapies, during which neither showed traces of HIV in their blood plasma and purified CD4+ T cells using a sensitive culture method (less than 3 copies/ml). The virus was once again detected in both patients some time after the discontinuation of therapy. In 2019, a British man became the second to be cleared of HIV after receiving a bone-marrow transplant from a virus-resistant (Δ32) donor. This patient is being called "the London patient" (a reference to the famous Berlin patient).


Multiple sclerosis

Since McAllister's 1997 report on a patient with multiple sclerosis (MS) who received a bone-marrow transplant for chronic myelogenous leukemia (CML), over 600 reports have been published describing HSCTs performed primarily for MS. These have been shown to "reduce or eliminate ongoing clinical relapses, halt further progression, and reduce the burden of disability in some patients" who have aggressive, highly active MS, "in the absence of chronic treatment with disease-modifying agents". A randomized clinical trial including 110 patients showed that HSCT significantly prolonged time to disease progression compared to disease-modifying therapy. Long-term outcome in patients with severe disease has showed that complete disease remission after HSCT is possible.


Other autoimmune neurological diseases

HSCT can also be used for treating selected, severe cases of other autoimmune neurological diseases such as
neuromyelitis optica Neuromyelitis optica spectrum disorders (NMOSD), including neuromyelitis optica (NMO), are autoimmune diseases characterized by acute inflammation of the optic nerve (optic neuritis, ON) and the spinal cord (myelitis). Episodes of ON and myelitis ...
,
chronic inflammatory demyelinating polyneuropathy Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensory function in the legs and arms. The disorder is sometimes called c ...
, and myasthenia gravis.


References


Further reading

*


External links


Bone marrow transplant – What happens
on NHS Choices * HCT-CI (Sorror et al. 2005
online calculator
{{DEFAULTSORT:Hematopoietic Stem Cell Transplantation Transplantation medicine Lymphology Hematology Surgical oncology Stem cells