Fas-dependent, activation-induced cell death of gamma delta cells

Activated gamma delta T cells undergo apoptosis upon restimulation of their T cell receptor (TCR)/CD3 complex. We demonstrate that in these cells, the activation-induced cell death (AICD) is mediated by Fas and Fas ligand (Fa sL) interaction. The activated gamma delta T cells are prone to AICD initia ted by exposure to mitogens, anti-TCR/CD3 antibodies, as well as specific a ntigens such as Daudi cells or ethyl pyrophosphate (Etpp). Cells that have been activated twice, and consequently more susceptible to AICD than primar y cells, display augmented tyrosine phosphorylation in comparison with cont rol cells. These studies outline a mechanism that may regulate gamma delta T cell activities in immune responses and limit the expansion of activated T cells repeatedly exposed to antigens.