![Blausen 0649 Monocyte (crop)](https://upload.wikimedia.org/wikipedia/commons/8/84/Blausen_0649_Monocyte_%28crop%29.png)
Monocytes are a type of leukocyte or
white blood cell
White blood cells, also called leukocytes or leucocytes, are the cell (biology), 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 de ...
. They are the largest type of leukocyte in blood and can
differentiate into
macrophage
Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...
s and conventional
dendritic cells. As a part of the
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
innate immune system
The innate, or nonspecific, immune system is one of the two main immunity strategies (the other being the adaptive immune system) in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is the ...
monocytes also influence
adaptive immune responses and exert tissue repair functions. There are at least three subclasses of monocytes in
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
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 ...
based on their phenotypic receptors.
Structure
Monocytes are
amoeboid
An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
in appearance, and have nongranulated
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
. Thus they are classified as
agranulocytes, although they might occasionally display some
azurophil granules
An azurophilic granule is a cellular object readily stainable with a Romanowsky stain. In white blood cells and hyperchromatin, staining imparts a burgundy or merlot coloration. Neutrophils in particular are known for containing azurophils l ...
and/or
vacuoles
A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...
. With a diameter of 15–22
μm, monocytes are the largest cell type in
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 ...
. Monocytes are mononuclear cells and the ellipsoidal nucleus is often lobulated/indented, causing a bean-shaped or kidney-shaped appearance. Monocytes compose 2% to 10% of all leukocytes in the human body.
Development
![Monoblast, promonocyte and monocyte](https://upload.wikimedia.org/wikipedia/commons/d/d6/Monoblast%2C_promonocyte_and_monocyte.jpg)
Monocytes are produced by the
bone marrow
Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic ce ...
from precursors called
monoblast
Monoblasts are the committed progenitor cells that differentiated from a committed macrophage or dendritic cell precursor (MDP) in the process of hematopoiesis. They are the first developmental stage in the monocyte series leading to a macrophage ...
s, bipotent cells that differentiated from
hematopoietic stem cells
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 ...
.
Monocytes circulate in the bloodstream for about one to three days and then typically migrate into tissues throughout the body where they differentiate into
macrophage
Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...
s and
dendritic cells.
Subpopulations
In humans
The first clear description of monocyte subsets by flow cytometry dates back to the late 1980s, when a population of
CD16
CD16, also known as FcγRIII, is a cluster of differentiation molecule found on the surface of natural killer cells, neutrophils, monocytes, macrophages, and certain T cells. CD16 has been identified as Fc receptors FcγRIIIa (CD16a) and FcγRI ...
-positive monocytes was described. Today, three types of monocytes are recognized in human blood:
# The classical monocyte is characterized by high level expression of the
CD14
CD14 (cluster of differentiation 14) is a human protein made mostly by macrophages as part of the innate immune system. It helps to detect bacteria in the body by binding lipopolysaccharide (LPS), a pathogen-associated molecular pattern (PAMP).
...
cell surface receptor (CD14
++ CD16
− monocyte)
# The non-classical monocyte shows low level expression of
CD14
CD14 (cluster of differentiation 14) is a human protein made mostly by macrophages as part of the innate immune system. It helps to detect bacteria in the body by binding lipopolysaccharide (LPS), a pathogen-associated molecular pattern (PAMP).
...
and additional co-expression of the
CD16
CD16, also known as FcγRIII, is a cluster of differentiation molecule found on the surface of natural killer cells, neutrophils, monocytes, macrophages, and certain T cells. CD16 has been identified as Fc receptors FcγRIIIa (CD16a) and FcγRI ...
receptor (CD14
+CD16
++ monocyte).
# The intermediate monocyte expresses high levels of
CD14
CD14 (cluster of differentiation 14) is a human protein made mostly by macrophages as part of the innate immune system. It helps to detect bacteria in the body by binding lipopolysaccharide (LPS), a pathogen-associated molecular pattern (PAMP).
...
and low levels of
CD16
CD16, also known as FcγRIII, is a cluster of differentiation molecule found on the surface of natural killer cells, neutrophils, monocytes, macrophages, and certain T cells. CD16 has been identified as Fc receptors FcγRIIIa (CD16a) and FcγRI ...
(CD14
++CD16
+ monocytes).
While in humans the level of CD14 expression can be used to differentiate non-classical and intermediate monocytes, the slan (6-Sulfo LacNAc) cell surface marker was shown to give an unequivocal separation of the two cell types.
Ghattas et al. state that the "intermediate" monocyte population is likely to be a unique subpopulation of monocytes, as opposed to a developmental step, due to their comparatively high expression of surface receptors involved in reparative processes (including
vascular endothelial growth factor
Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...
receptors type 1 and 2,
CXCR4
C-X-C chemokine receptor type 4 (CXCR-4) also known as fusin or CD184 (cluster of differentiation 184) is a protein that in humans is encoded by the ''CXCR4'' gene. The protein is a CXC chemokine receptor.
Function
CXCR-4 is an alpha-chemokin ...
, and
Tie-2
The angiopoietin receptors are receptors that bind angiopoietin.
TIE-1 and TIE-2 comprise the cell-surface receptors that bind and are activated by the angiopoietins, (Ang1, Ang2, Ang3, Ang4). The angiopoietins are protein growth factors r ...
) as well as evidence that the "intermediate" subset is specifically enriched in the bone marrow.
In mice
In mice, monocytes can be divided in two subpopulations. Inflammatory monocytes (
CX3CR1
CX3C motif chemokine receptor 1 (CX3CR1), also known as the fractalkine receptor or G-protein coupled receptor 13 (GPR13), is a transmembrane protein of the G protein-coupled receptor 1 (GPCR1) family and the only known member of the CX3C chemokin ...
low,
CCR2
C-C chemokine receptor type 2 (CCR2 or CD192 (cluster of differentiation 192) is a protein that in humans is encoded by the ''CCR2'' gene. CCR2 is a CC chemokine receptor.
Gene
This CCR2 gene is located in the chemokine receptor gene cluster ...
pos,
Ly6Chigh,
PD-L1
Programmed death-ligand 1 (PD-L1) also known as cluster of differentiation 274 (CD274) or B7 homolog 1 (B7-H1) is a protein that in humans is encoded by the ''CD274'' gene.
Programmed death-ligand 1 (PD-L1) is a 40kDa type 1 transmembrane protei ...
neg), which are equivalent to human classical CD14
++ CD16
− monocytes and resident monocytes (
CX3CR1
CX3C motif chemokine receptor 1 (CX3CR1), also known as the fractalkine receptor or G-protein coupled receptor 13 (GPR13), is a transmembrane protein of the G protein-coupled receptor 1 (GPCR1) family and the only known member of the CX3C chemokin ...
high,
CCR2
C-C chemokine receptor type 2 (CCR2 or CD192 (cluster of differentiation 192) is a protein that in humans is encoded by the ''CCR2'' gene. CCR2 is a CC chemokine receptor.
Gene
This CCR2 gene is located in the chemokine receptor gene cluster ...
neg,
Ly6Clow,
PD-L1
Programmed death-ligand 1 (PD-L1) also known as cluster of differentiation 274 (CD274) or B7 homolog 1 (B7-H1) is a protein that in humans is encoded by the ''CD274'' gene.
Programmed death-ligand 1 (PD-L1) is a 40kDa type 1 transmembrane protei ...
pos), which are equivalent to human non-classical CD14
+ CD16
+ monocytes. Resident monocytes have the ability to patrol along the endothelium wall in the steady state and under inflammatory conditions.
Function
Monocytes are mechanically active cells and migrate from blood to an inflammatory site to perform their functions. As explained before, they can differentiate into macrophages and dendritic cells, but the different monocyte subpopulations can also exert specific functions on their own. In general, monocytes and their macrophage and dendritic cell progeny serve three main functions in the immune system. These are
phagocytosis
Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...
, antigen presentation, and
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
production.
Phagocytosis
Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...
is the process of uptake of microbes and particles followed by digestion and destruction of this material. Monocytes can perform phagocytosis using intermediary (
opsonising) proteins such as
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
or
complement
A complement is something that completes something else.
Complement may refer specifically to:
The arts
* Complement (music), an interval that, when added to another, spans an octave
** Aggregate complementation, the separation of pitch-clas ...
that coat the pathogen, as well as by binding to the microbe directly via
pattern recognition receptors
Pattern recognition receptors (PRRs) play a crucial role in the proper function of the innate immune system. PRRs are germline-encoded host sensors, which detect molecules typical for the pathogens. They are proteins expressed, mainly, by cells of ...
that recognize pathogens. Monocytes are also capable of killing infected host cells via
antibody-dependent cell-mediated cytotoxicity
Antibody-dependent cellular cytotoxicity (ADCC), also referred to as antibody-dependent cell-mediated cytotoxicity, is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system actively lyses a target cell, whose ...
.
Vacuolization
Vacuolization is the formation of vacuoles or vacuole-like structures, within or adjacent to cells. Perinuclear vacuolization of epidermal keratinocytes is most likely inconsequential when not observed in combination with other pathologic find ...
may be present in a cell that has recently phagocytized foreign matter.
Differentiation into other effector cells
Monocytes can migrate into tissues and replenish resident
macrophage
Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...
populations. Macrophages have a high antimicrobial and phagocytic activity and thereby protect tissues from foreign substances. They are cells that possess a large smooth nucleus, a large area of cytoplasm, and many internal
vesicles
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane
* Synaptic vesicle
; In human embryology
* Vesicle (embryology), bulge-like features o ...
for processing foreign material. Although they can be derived from monocytes, a large proportion is already formed prenatally in the
yolk sac
The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is ...
and foetal liver.
''In vitro'', monocytes can differentiate into
dendritic cells
Dendritic cells (DCs) are antigen-presenting cells (also known as ''accessory cells'') of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. The ...
by adding the cytokines
granulocyte macrophage colony-stimulating factor
Granulocyte-macrophage colony-stimulating factor (GM-CSF), also known as colony-stimulating factor 2 (CSF2), is a monomeric glycoprotein secreted by macrophages, T cells, mast cells, natural killer cells, endothelial cells and fibroblasts th ...
(GM-CSF) and
interleukin 4
The interleukin 4 (IL4, IL-4) is a cytokine that induces differentiation of naive helper T cells ( Th0 cells) to Th2 cells. Upon activation by IL-4, Th2 cells subsequently produce additional IL-4 in a positive feedback loop. IL-4 ...
.
Such monocyte-derived cells do, however, retain the signature of monocytes in their
transcriptome
The transcriptome is the set of all RNA transcripts, including coding and non-coding, in an individual or a population of cells. The term can also sometimes be used to refer to all RNAs, or just mRNA, depending on the particular experiment. The t ...
and they cluster with monocytes and not with bona fide dendritic cells.
Specific functions of monocyte subpopulations
Aside from their differentiation capacity, monocytes can also directly regulate immune responses. As explained before, they are able to perform phagocytosis. Cells of the classical subpopulation are the most efficient phagocytes and can additionally secrete inflammation-stimulating factors. The intermediate subpopulation is important for
antigen presentation
Antigen presentation is a vital immune process that is essential for T cell immune response triggering. Because T cells recognize only fragmented antigens displayed on cell surfaces, antigen processing must occur before the antigen fragment, n ...
and
T lymphocyte
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 rec ...
stimulation. Briefly, antigen presentation describes a process during which microbial fragments that are present in the monocytes after phagocytosis are incorporated into MHC molecules. They are then trafficked to the cell surface of the monocytes (or macrophages or dendritic cells) and presented as antigens to activate T lymphocytes, which then mount a specific immune response against the antigen. Non-classical monocytes produce high amounts of pro-inflammatory
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
s like
tumor necrosis factor
Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolog ...
and
interleukin-12
Interleukin 12 (IL-12) is an interleukin that is naturally produced by dendritic cells, macrophages, neutrophils, and human B- lymphoblastoid cells ( NC-37) in response to antigenic stimulation. IL-12 belongs to the family of interleukin-12. ...
after stimulation with microbial products. Furthermore, a monocyte patrolling behavior has been demonstrated in humans both for the classical and the non-classical monocytes, meaning that they slowly move along the
endothelium
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
to examine it for pathogens. Said et al. showed that activated monocytes express high levels of
PD-1
Programmed cell death protein 1, also known as PD-1 and CD279 (cluster of differentiation 279), is a protein on the surface of T and B cells that has a role in regulating the immune system's response to the cells of the human body by down-regula ...
which might explain the higher expression of PD-1 in CD14
+CD16
++ monocytes as compared to CD14
++CD16
− monocytes. Triggering monocytes-expressed PD-1 by its
ligand
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...
PD-L1 induces IL-10 production, which activates
CD4 Th2 cells
The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considere ...
and inhibits
CD4 Th1 cell
The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are consider ...
function.
Many factors produced by other cells can regulate the
chemotaxis
Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemica ...
and other functions of monocytes. These factors include most particularly
chemokines
Chemokines (), or chemotactic cytokines, are a family of small cytokines or signaling proteins secreted by cells that induce directional movement of leukocytes, as well as other cell types, including endothelial and epithelial cells. In addition ...
such as
monocyte chemotactic protein-1 (CCL2) and
monocyte chemotactic protein-3 (CCL7); certain
arachidonic acid metabolites such as
leukotriene B4
Leukotriene B4 (LTB4) is a leukotriene involved in inflammation. It has been shown to promote insulin resistance in obese mice.
Biochemistry
Leukotriene B4 (LTB4) is a leukotriene involved in inflammation. It is produced from leukocytes in r ...
and members of the
5-hydroxyicosatetraenoic acid and 5-oxo-eicosatetraenoic acid family of OXE1 receptor agonists (e.g.,
5-HETE and 5-oxo-ETE); and
N-Formylmethionine leucyl-phenylalanine and other N-formylated
oligopeptides
An oligopeptide, often just called peptide ('' oligo-'', "a few"), consists of two to twenty amino acids and can include dipeptides, tripeptides, tetrapeptides, and pentapeptides. Some of the major classes of naturally occurring oligopeptides inc ...
which are made by bacteria and activate the
formyl peptide receptor 1
Formyl peptide receptor 1 (FPR1, FPR1 receptor, fMet-Leu-Phe receptor 1, FMLP receptor 1, or N-formylmethionyl-leucyl-phenylalanine receptor 1) is a cell surface receptor protein that in humans is encoded by the ''formyl peptide receptor 1'' (''F ...
.
Other microbial products can directly activate monocytes and this leads to production of pro-inflammatory and, with some delay, of anti-inflammatory
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
s. Typical cytokines produced by monocytes are
TNF
Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolog ...
,
IL-1, and
IL-12.
Clinical significance
A ''monocyte count'' is part of a
complete blood count
A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide cytometry, information about the cells in a person's blood. The CBC indicates the counts of white blood cells, red blood cell ...
and is expressed either as a percentage of monocytes among all white blood cells or as absolute numbers. Both may be useful, but these cells became valid diagnostic tools only when monocyte subsets are determined.
Monocytic cells may contribute to the severity and disease progression in COVID-19 patients.
Monocytosis
Monocytosis
Monocytosis is an increase in the number of monocytes circulating in the blood. Monocytes are white blood cells that give rise to macrophages and dendritic cells in the immune system.
In humans, monocytosis occurs when there is a sustained rise i ...
is the state of excess monocytes in the peripheral blood. It may be indicative of various disease states.
Examples of processes that can increase a monocyte count include:
*
chronic inflammation
Chronic systemic inflammation (SI) is the result of release of pro-inflammatory cytokines from immune-related cells and the chronic activation of the innate immune system. It can contribute to the development or progression of certain conditions ...
*
diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
*
stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
response
*
Cushing's syndrome
Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a ...
(hyperadrenocorticism)
*
immune-mediated disease
An immune disorder is a dysfunction of the immune system. These disorders can be characterized in several different ways:
* By the component(s) of the immune system affected
* By whether the immune system is overactive or underactive
* By whether t ...
*
granulomatous disease
*
atherosclerosis
Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
*
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
*
red blood cell
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
regeneration
*
viral fever
Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...
*
sarcoidosis
Sarcoidosis (also known as ''Besnier-Boeck-Schaumann disease'') is a disease involving abnormal collections of inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph nodes. Less commonly af ...
*
chronic myelomonocytic leukemia
Chronic myelomonocytic leukemia (CMML) is a type of leukemia, which are cancers of the blood-forming cells of the bone marrow. In adults, blood cells are formed in the bone marrow, by a process that is known as haematopoiesis. In CMML, there are i ...
(CMML)
A high count of CD14
+CD16
++ monocytes is found in severe infection (
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 ...
).
In the field of atherosclerosis, high numbers of the CD14
++CD16
+ intermediate monocytes were shown to be predictive of cardiovascular events in populations at risk.
CMML is characterized by a persistent monocyte count of > 1000/microL of blood. Analysis of monocyte subsets has demonstrated predominance of classical monocytes and absence of CD14lowCD16+ monocytes. The absence of non-classical monocytes can assist in diagnosis of the disease and the use of slan as a marker can improve specificity.
Monocytopenia
Monocytopenia
Monocytopenia is a form of leukopenia associated with a deficiency of monocytes.
It has been proposed as a measure during chemotherapy to predict neutropenia, though some research indicates that it is less effective than lymphopenia.
Causes
The ...
is a form of
leukopenia
Leukopenia () is a decrease in the number of leukocytes (WBC). Found in the blood, they are the white blood cells, and are the body's primary defense against an infection. Thus the condition of leukopenia places individuals at increased risk of inf ...
associated with a deficiency of monocytes.
A very low count of these cells is found after therapy with immuno-suppressive
glucocorticoids
Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebr ...
.
Also, non-classical slan+ monocytes are strongly reduced in patients with
hereditary diffuse leukoencephalopathy with spheroids, a neurologic disease associated with mutations in the macrophage colony-stimulating factor receptor gene.
Blood content
See also
*
Complete blood count
A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide cytometry, information about the cells in a person's blood. The CBC indicates the counts of white blood cells, red blood cell ...
*
Hematopoiesis
Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells ...
*
Lymphocyte
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic ad ...
*
Neutrophil granulocyte
*
Phagocyte
Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek ', "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek ...
References
External links
*
Human Monocytes — Prof. Dr. Ziegler-HeitbrockCirculation of Body Fluids
{{Authority control
Mononuclear phagocytes
Immune system
Cell biology
Human cells