Activated B cells express functional Fas ligand

Abstract

Abstract Fas ligand (FasL, Apo‐1L) is a member of the tumor necrosis factor protein family and binding to its receptor (Fas, Apo‐1, CD95) triggers cell death through apoptosis. Ligand expression is restricted to cells with known cytolytic activity and found on hematopoietic cells of the T cell and natural killer lineage. Here we provide evidence that B lymphocytes can express FasL. Flow cytometric analysis revealed that FasL is expressed on the surface of B cells upon stimulation with either lipopolysaccharide or phorbol 12‐myristute 13‐acetate/ionomycin. FasL expression on activated B cells was confirmed by Western blot and reverse transcriptase polymerase chain reaction analysis. FasL on B cells is functional since lipopolysaccharide‐activated B lymphocytes derived from wild type, but not from g/d mutant mice, were able to kill Fas‐sensitive target cells. Our data suggest that the Fas system may contribute to the control of B cell homeostasis.