THE PHYSIOLOGY OF BCL-2 EXPRESSION IN MURINE B-LYMPHOCYTES

Quantitation of bcl-2 gene expression in B-lineage lymphocytes from no rmal adult mice allows the identification of four cell populations, ch aracterized by successive three- to fivefold increases in average mRNA levels: bone marrow pre-B cells, bone marrow B cells, splenic B cells and long-lived splenic B cells. Thus, in line with previous experimen ts using overexpression systems, a correlation between longevity and l evels of bcl-2 mRNA exists also in the physiology of B-lineage cells. The data are compatible with a quantitative regulation of expression, possibly determined at selective differentiation steps. No difference in bcl-2 expression was detected by comparing splenic IgD+ with IgD- B cells, while distinctly low levels of bcl-2 mRNA were scored in perit oneal CD5+ and CD5- B cells. These observations indicate that the repo rted persistence of peritoneal B cells may be controlled by mechanisms other than bcl-2 gene expression.