__NOTOC__ A lymphoblast is a modified naive

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 a ...

with altered cell morphology. It occurs when the lymphocyte is activated by an antigen (from antigen-presenting cells) and increased in volume by nucleus and cytoplasm growth as well as new mRNA and protein synthesis. The lymphoblast then starts dividing two to four times every 24 hours for three to five days, with a single lymphoblast making approximately 1000 clones of its original naive lymphocyte, with each clone sharing the originally unique antigen specificity. Finally the dividing cells differentiate into effector cells, known as plasma cells (for B cells), cytotoxic T cells, and helper T cells. Lymphoblasts can also refer to immature cells which typically differentiate to form mature

s. Normally lymphoblasts are found in the bone marrow, but in

acute lymphoblastic leukemia Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruis ...

(ALL), lymphoblasts proliferate uncontrollably and are found in large numbers in the peripheral blood. The size is between 10 and 20 μm. Although commonly lymphoblast refers to a precursor cell in the maturation of

leukocyte 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 ...

s, the usage of this term is sometimes inconsistent. The Chronic Lymphocytic Leukemia Research Consortium defines a lymphoblast as "A lymphocyte that has become larger after being stimulated by an antigen. Lymphoblasts look like immature lymphocytes, and were once thought to be precursor cells."CRC – Glossary L
Commonly, when speaking about leukemia, "blast" is used as an abbreviation for lymphoblasts. Lymphoblasts can be distinguished microscopically from

myeloblast The myeloblast is a unipotent stem cell which differentiates into the effectors of the granulocyte series. It is found in the bone marrow. Stimulation of myeloblasts by G-CSF and other cytokines triggers maturation, differentiation, proliferation ...

s by having less distinct nucleoli, more condensed chromatin, and an absence of cytoplasmic granules. However these morphologic distinctions are not absolute and a definitive diagnosis relies on antibody

immunostaining In biochemistry, immunostaining is any use of an antibody-based method to detect a specific protein in a sample. The term "immunostaining" was originally used to refer to the immunohistochemical staining of tissue sections, as first described by ...

for the presence of unique

cluster of differentiation The cluster of differentiation (also known as cluster of designation or classification determinant and often abbreviated as CD) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophen ...

receptors.

Additional images

Image:Illu blood cell lineage.jpg, Blood cell lineage

References

Blood cells Colony forming units {{oncology-stub

Additional images

See also

References