ACTIVATION-INDUCED DEATH OF MATURE T-CELLS IN THE REGULATION OF IMMUNE-RESPONSES

Deletion of self-reactive clones of immature thymocytes by activation- induced death (AID) is thought to be the primary mechanism for the est ablishment of self-tolerance in the T-cell compartment. Recent evidenc e suggests that a genetically distinct but analogous process of AID in mature T cells is important in regulating peripheral immune responses . AID of peripheral T cells requires the expression of functional Fas and Fas ligand by the T-cell population. As qualitatively similar sign als from the TCR are responsible for both T-cell expansion in inflamma tion and T-cell elimination by AID, regulating the balance between the se opposing functions plays a crucial role in successful responses to pathogens and tumors while minimizing autoimmunity.