CD95 mediated T cell apoptosis and its relevance to immune deviation

The CD95/CD95L pair plays a manifold role in regulating life and death in the function of the immune system. Examples include CD95/CD95L acting as cytotoxic CD8+ T cell effector molecules, or functioning on CD4+ T helper cells to maintain peripheral tolerance or reestablishing homeostasis. Current understanding of the CD95 signaling pathway reveals several potential regulatory targets, acting both receptor proximally and distally, that can terminate or amplify the receptor's signal. The important and possibly non-redundant role of CD95 is highlighted both in how deficiencies in functional CD95 or its ligand manifest themselves in autoimmune syndromes, and how uncontrolled cell death results in insufficient, or inappropriate immune responses against immune challenge. This review examines CD95-mediated signal transduction, and the effect preferential apoptosis of T helper cell subsets has on immune system biasing.