Activation of the alternative pathway of complement by apoptotic Jurkat cells.

Jurkat T cells die of apoptosis upon exposure to anti-Fas mAb. Here we show that although the alternative complement pathway generally does not attack homologous cells, anti-Fas-induced apoptotic Jurkat T cells were attacked antibody-independently by the alternative pathway of human complement and opsonized with iC3b, which is a ligand of the complement receptor type 3 (CR3) of phagocytes. These results suggest that apoptotic cells become the targets of the homologous alternative complement pathway, which facilitates the clearance of apoptotic cells by phagocytes.