Leu-1+ (CD5+) B cells. A major lymphoid subpopulation in human fetal spleen: phenotypic and functional studies.
Examination of the cell surface phenotype of fetal splenic lymphocytes demonstrated a major, novel subpopulation of B cells that co-express Leu-1 (CD5) in addition to B cell differentiation antigens (Leu-1+ B cells). These cells are similar to some conventional B cells in that they express HLA-DR, Leu-12, and B1, as well as both immunoglobulin (Ig) M and IgD. They comprise 40 to 60% of total splenic B cells in the fetus but are infrequent in fetal liver and adult spleen. Fetal Leu-1+ B cells do not respond to pokeweed mitogen with either proliferation or Ig secretion, and in contrast to the murine counterpart, Ly-1 B cells, they do not constitutively produce Ig. Leu-1+ B cells were incapable of augmenting Ig production of Leu-1- B cells when suboptimal numbers of T cells were present; however, they did require the presence of T cells to secrete antibody. They do not cap either the CD5 protein or surface Ig. These cells are a unique subpopulation of fetal splenic B cells that do not function as conventional B cells. Their role in the humoral immune response is unknown. They may represent the normal stage of B cell development, which is reflected in the phenotype of B cell CLL cells.
D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm / Q000032:analysis; D001402:B-Lymphocytes / Q000145:classification* / Q000276:immunology / Q000378:metabolism; D005333:Fetus / Q000276:immunology*; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D006801:Humans; D007072:Immunoglobulin D / Q000032:analysis; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000032:analysis / Q000096:biosynthesis; D008222:Lymphokines / Q000032:analysis*; D015260:Neprilysin; D010641:Phenotype; D011947:Receptors, Antigen, B-Cell / Q000032:analysis; D013154:Spleen / Q000166:cytology*
D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008222:Lymphokines; D011947:Receptors, Antigen, B-Cell; D015260:Neprilysin