Immature B cells from human and mouse bone marrow can change their surface light chain expression.
The capacity of bone marrow-derived surface immunoglobulin-positive (sIg+) human and mouse immature B cells, generated either in vitro or in vivo, to change their light (L) chain expression, has been assayed by the number of cells which change in vitro from one type of L chain to the other type, or to no sIg at all. Immature sIg+ B cells were generated in vitro from sIg- precursor cells from human or mouse bone marrow. The immature sIg+ cells expressed RAG-1. Human sIg+ cells expressed kappa and lambda L chains in ratios between 1:1 and 3:1, whereas in mouse cells, this ratio ranged from 10:1 to 20:1. Upon reculture of the human and mouse kappa+ sIg+ cells, about half of them remained kappa+, a quarter became lambda+, and another quarter became sIg-. Between 1 and 3% expressed both kappa and lambda chains. Of the human lambda+ cells, about two-thirds remained lambda+, only 1 to 2% became kappa+, while the other third became sIg-. Again, between 1 and 3% expressed both kappa and lambda L chains. These results indicate that expression of sIgM in the B cell membrane does not terminate L chain gene rearrangement, and that some order exists in kappa versus lambda gene rearrangements. Hence, human and mouse kappa+ immature B cells can become lambda+, but very few of the lambda+ cells can become kappa+, and both can become sIg-. Further, human CD10+/sIg+ kappa+ and lambda+ cells and mouse B220low/sIglow kappa+ cells enriched from bone marrow, i.e. immature B cells differentiated in vivo, changed their Ig phenotype upon in vitro culture, but in lower frequencies. By contrast, human and mouse mature B cells did not change their L chain or Ig phenotype. Hence, at least a part of the sIg+ immature B cells in bone marrow retain the capacity to change their L chain and Ig phenotype, and this capacity is lost when they become mature, peripheral B cells.
D000293:Adolescent; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D001854:Bone Marrow Cells; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D018076:DNA, Complementary / Q000032:analysis; D015322:Gene Rearrangement, B-Lymphocyte / Q000276:immunology*; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000096:biosynthesis* / Q000235:genetics; D007075:Immunoglobulin M / Q000096:biosynthesis; D007223:Infant; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008875:Middle Aged; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis
D018076:DNA, Complementary; D007147:Immunoglobulin Light Chains; D007075:Immunoglobulin M; D012333:RNA, Messenger