Cell-cycle kinetics of proliferating mouse B lymphocytes in vitro

Resting mouse B lymphocytes were stimulated in vitro with lipopolysaccharide, Sepharose-coupled anti-kappa antibodies or a combination of the two. B lymphocytes stimulated with anti-kappa entered the cell-cycle with more rapid kinetics and at a higher frequency than did the corresponding cell population stimulated with lipopolysaccharide. Using cell cycle analysis after DNA staining combined with an M phase block, the cell-cycle kinetics of in vitro cultured B-lymphocytes was studied. The labelling index of lipopolysaccharide stimulated B lymphocytes was 60% while that for anti-kappa Sepharose stimulated cells was 85%. The generation time of the actively cycling population from both types of cultures was constant and was of the order of 18 h. Thus, the fraction of B lymphocytes induced to proliferate in vitro varies depending on the stimulus, while the growth kinetics of the actively proliferating populations are remarkably constant.