The FAS antigen (CD95) is a 40-50 kDa cell surface glycoprotein that belongs to the nerve growth factor/tumor necrosis factor (TNF) receptor family. FAS is a receptor for TNFSF6/FASL. The adaptor molecule FADD recruits caspase-8 to the activated receptor. The resulting death-inducing signaling comple, Xenopus/Amphibian, (DISC) performs caspase-8 proteolytic activation which initiates the subsequent cascade of caspases (asparte-specific cysteine proteases) mediating apoptosis. FAS-mediated apoptosis may have a role in the induction of peripheral tolerance in the antigen-stimulated suicide of mature T-cells or both. Defects in FAS are the cause of autoimmune lymphoproliferative syndrome type 1A (ALPS1A), a childhood syndrome involving hemolytic anemia and thrombocytopenia.