There are two broad populations of B cells, B-1 and B-2. B-1 cells are the primary B cell during fetal and neonatal development. These cells can self-renew and localize mainly in the peritoneal and pleural cavities. B-1 cells produce the majority of “natural” antibodies, immunoglobulin (Ig) M and IgA. Natural antibodies exist in the blood of healthy individuals before immunization, are the first line of defense against pathogens (disease-causing antigens), and they also influence T cell expansion.
B-2 cells are constantly produced from bone marrow precursors, circulate in the blood, and are found in secondary lymphoid tissues (e.g., lymph nodes, spleen, etc.). Cells arising from the B-2 lineage (follicular and marginal zone B cells) can respond to numerous types of T-dependent and T-independent antigens. Also, B-2 cells produce high-affinity antibodies during an infection.
Mouse B-1 and B-2 cells develop from different progenitors (parent cells). The origins of human B-1 and B-2 cells have been difficult to determine. However, a group of researchers from the Feinstein Institute of Medical Research conducted studies in order to determine human B-1 and B-2 cell progenitors. They did this by separating CD34 stem cells lacking lineage markers (Lin¯CD34+) into Lin¯CD34+CD38lo (expressing an intermediate to low level of CD38 antigen) and Lin¯CD34+CD38hi (expressing high CD38 levels) cell populations.
Transplanted Lin¯CD34+CD38lo cells produced CD19+ B cells (essential in antigen-specific immune response) after transfer into immunodeficient humanized mice. These CD19+ B cells were found in various tissues of the mice including the spleen and bone marrow, and exhibited the B-1 or the B-2 cell phenotypes. This suggests that the B-1 and B-2 cells arise from a common progenitor, Lin¯CD34+CD38lo stem cells. A better understanding of B cell development and function can provide valuable insights into the development of many diseases and the discovery of new and effective immunotherapies.
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Quách TD, et al. "Human B-1 And B-2 B Cells Develop From Lin-CD34+Cd38lo Stem Cells. - Pubmed - NCBI". Ncbi.nlm.nih.gov. N.p., 2016. Web. 28 Nov. 2016.