Phosphorylation of Bcl-2 and mitochondrial changes are associated with apoptosis of lymphoblastoid cells induced by normal immunoglobulin G

Normal human immunoglobulin Gr induces apoptosis in human lymphoblastoid ce lls which involves antibody-mediated Fas ligation and the activation of cas pases, Here, we show that Bcl-2 is phosphorylated on serine upon treatment of CEM T cells with normal IgG and that the overexpression of Bcl-2 in stab le transfectants of CEM T cells prevents IgG-induced cell death. Treatment of CEM cells with normal IgG also results in a reduction in mitochondrial t ransmembrane potential and in the release of cytochrome c (Cyt c) into cyto sol. The findings are concordant with earlier observations that apoptosis i nduced by IgG is associated with the activation of caspases. Our results de monstrate that Bcl-2 controls apoptosis induced by normal IgG and support a central role for Bcl-2 and mitochondria in antibody-mediated selection of lymphocyte repertoires. (C) 1999 Academic Press.