INDUCTION OF LFA-1 INDEPENDENT HUMAN B-CELL PROLIFERATION AND DIFFERENTIATION BY BINDING OF CD40 WITH ITS LIGAND

Engagement of CD40 on resting B cells in the presence of IL-4 triggers B cell proliferation, differentiation and homotypic adhesion. This st udy was designed to investigate the role of LFA-1/ICAM-1 interactions in homotypic adhesion and proliferation of CD40-activated human B lymp hocytes. Freshly isolated B cells were cultured in vitro in the presen ce of IL-4 and of L cells expressing CD40L, the CD40 ligand. The addit ion to the culture medium of LFA-1 and ICAM-1 antibodies inhibited hom otypic B lymphocyte adhesion. However, these antibodies failed to affe ct B lymphocyte proliferation and antibody production. These results i ndicate that aggregation and proliferation are independent events alth ough both induced by CD40 activation.