Immunological senescence. II. Normal in vitro colony formation by B cells from old mice.

The in vitro frequency and proliferative capacity of B cells and B-cell precursors in old mice was assessed. The mitogenic response to the B-cell mitogens lipopolysaccharide (LPS) and dextran sulphate decline later and at a slower rate than the T-cell response to phytohaemagglutinin and concanavalin A. The response to precursor B-cell mitogen dextran sulphate was not depressed in the bone marrow of aging mice. In addition, the dose response and kinetics of LPS and mercaptoethanol stimulated B-cell colony formation in agar was identical in spleen cells from young and old mice. These results indicate that the intrinsic proliferative capacity of B cells from old mice is normal.