CD80 (B7.1) and CD86 (B7.2) induce EBV-transformed B cell apoptosis through the Fas/FasL pathway

CD80 and CD86 expression is strongly regulated in B cells and is induced by various stimuli (e.g., cytokines, ligation of MHC class II and CD40 ligand). Epstein-Barr virus (EBV) infection activates B lymphocytes and transforms them into lymphoblastoid cells. However, the role of CD80 and CD86 in EBV infection of B cells remains unclear. Here, we observed that cross-linking of CD80 and CD86 in EBV-transformed B cells induced apoptosis through caspase-dependent release of apoptosis-related molecules, cytochrome c and apoptosis-inducing factor (AIF) from mitochondria, because Z-VAD-fmk (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone) and N-acetylcysteine (NAC) blocked apoptosis and disruption of mitochondria. Stimulation of CD80 and CD86 induced expression of Fas ligand (FasL) on EBV-transformed B cells and upregulated Fas and FasL expression in IM-9 cells. Apoptosis through Fas-FasL interactions was blocked by treatment of cells with ZB4, an antagonistic anti-Fas antibody. These results suggest that the co-stimulatory molecules CD80 and CD86 induced by EBV infection stimulate apoptosis of EBV-transformed lymphoblastoid B cells via the Fas/FasL pathway.