Fig. 4

Intrinsic pathway of lymphocyte apoptosis and its effects on immune function. Cytochrome c is released from the mitochondria and, together with apoptotic protease-activating factor 1 (APAF1) and pro-caspase-9, form the apoptosome, which triggers apoptosis (intrinsic or mitochondrial pathway). In addition to lymphocyte depletion, apoptosis impairs immunity by inducing immunosuppression of the surviving cells. Monocytes/macrophages that ingest apoptotic cells show reduced HLA-DR expression, compromising their antigen-presenting function [29]