Ontogeny, distribution and function of CD38-expressing B lymphocytes in mice

Analysis of expression of CD38, CD45R (B220), IgM and IgD an splenic B lymp hocytes from mice of different ages demonstrated CD38 an both immature (B22 0(+), BCR-) and mature (B220(+), BCR+) B lymphocytes. Similarly, CD38 is ex pressed as early as B220 on the surface of progenitor B cells in the bone m arrow. In spite of expressing of CD38 and IgM, neonatal B cells, in contras t to the adult, failed to proliferate to either anti-CD38 or anti-IgM, cros slinking when IL-4 was present. They did, however, respond to LPS and anti- CD40, and by 2 weeks of age they began to respond to anti-CD38 and anti-IgM , reaching adult B cell levels by 4 weeks. Although the distribution of CD3 8 on adult B cells from most different lymphoid compartments was broadly si milar, significantly higher levels of CD38 were expressed on peritoneal B l ymphocytes. A detailed analysis, using IgM/IgD ratio and staining with anti -CD5 confirmed that B1 lymphocytes were expressing a high level of CD38. In terestingly, both immature B cells and peritoneal B1 lymphocytes were unres ponsive to anti-CD38. However, they were activated by LPS or anti-CD40.