INDUCTION OF BCL-X BY CD40 ENGAGEMENT RESCUES SLG-INDUCED APOPTOSIS IN MURINE B-CELLS

CD40L, a membrane protein of activated T cells, interacts with the B c ell receptor CD40, This interaction has been implicated in the rescue of germinal center B cells from apoptosis and in the rescue of WEHI-23 1 B lymphoma cells from sig-induced apoptosis, In this report, we have demonstrated that the signal mediated by CD40L acts upon bcl-x, a bcl -2 homologue, bcl-x expression is strongly enhanced by CD40 receptor e ngagement, while there is little or no induction by sig cross-linking, The expression of bar and bcl-2 is not significantly affected by eith er CD40L or sig crosslinking, Antisense but not sense phosphorothioate oligonucleotide for bcl-x can partially block this CD40-mediated apop totic rescue, This result suggests that the up-regulation of bcl-x by CD40L plays an important role in CD40-mediated apoptotic rescue in mur ine B cells.