title: Studies on the generation of B lymphocytes in fetal liver and bone marrow.
abstract: With the use of immunofluorescence techniques, cells containing cytoplasmic IgM (cIgM+), but lacking detectable surface IgM (sIgM+), have been identified in mouse fetal liver and adult bone marrow as a distinct cell population to sIgM+ B lymphocytes. We have shown that there is a considerable difference in the rate of entry of cIgM+ and sIgM+ cells into DNA synthesis in these locations. Moreover, within the cIgM+ population, the largest cells are the main group entering DNA synthesis. Our results are compatible with the notion that a pool of rapidly proliferating, large cIgM+ cells is present in fetal liver and adult bone marrow and that these cells give rise to populations of smaller cIgM+ cells, which move out of cell cycle, and convert to sIgM+ B lymphocytes. However, we recognize that this interpretation is speculative. Finally, we have shown that fetal bone marrow is a site of generation of sIgM+ B lymphocytes, but the question as to whether these cells are derived from Ig- precursors within marrow itself remains open.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D001853:Bone Marrow / Q000276:immunology*; D001854:Bone Marrow Cells; D002478:Cells, Cultured; D003593:Cytoplasm / Q000276:immunology; D005260:Female; D005333:Fetus / Q000276:immunology; D007075:Immunoglobulin M / Q000378:metabolism; D008099:Liver / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011247:Pregnancy; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors
chemical_list: D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell; D013936:Thymidine