Dendritic cells (DC) are the professional antigen presenting cells that process and present antigens to lymphocytes [1]. It was demonstrated that DC migrate to the lymph node to activate naive T cells and are eliminated by antigen-specific T cells within 48 hours of arriving at the lymph node [3]. This T cell directed DC elimination led to yet another mechanism of regulating the immune system through DC apoptosis [4]. DC apoptosis occurs by either cytokine deprivation or by antigen-specific T lymphocytes [4, 5]. DC can be killed by T cells through Fas or perforin and granzyme B [4, 6]. Furthermore, deprivation of the cytokine GM-CSF from DC induces the down-regulation of an antiapoptotic protein Bcl-2 that results in the disruption of the mitochondrial membrane [7]. It was also demonstrated that over-expression of the anti-apoptotic Bcl-2 increases the lifespan of DC in vivo [8]. The disruption of mitochondrion plays an important role in regulating apoptosis induced by cytokine deprivation, granzyme B, and Fas signaling [9-11]. The regulation of the mitochondrial membrane integrity is controlled by the ratio of the pro and anti-apoptotic BCL-2 family members [2]. Because Bcl-2 and Bax play important roles in regulating the integrity of mitochondrion membrane, I hypothesize that Bax and Bcl-2 are important regulators of DC apoptosis. ? ?
