Up-regulation of c-FLIPshort and Reduction of Activation-Induced Cell Death in T-cells from Patients with Type 1 Diabetes

Abstract

AICD of T-cells is an efficient way of removing activated T-lymphocytes. In this study we investigated the molecular basis of AICD upon reactivation in peripheral T-lymphocytes from newly diagnosed T1DM patients and age-matched healthy controls. In an in vitro model system, PHA-stimulated T-cells, upon prolonged culture in IL-2, acquire a sensitive phenotype to Fas-mediated apoptosis. This phenomenon is less pronounced in T1DM T-cells. Moreover, the restimulation of activated T-cells via TCR/CD3 and/or via CD28 inhibits Fas-mediated apoptosis in T1DM in comparison to control T-cells. After Fas triggering, the generation of the active sub-units of caspase-8 is significantly reduced in T1DM T-cells restimulated via TCR/CD3 and/or CD28. In parallel, we found that the amount of c-FLIPshort protein is significantly increased in the DISC only in T1DM T-cells restimulated via TCR/CD3 and via CD28. These data suggest that increased levels of c-FLIPshort may prevent recruitment of pro-caspase-8 in T1DM CD3-treated T-cells and provide new insight into the molecular mechanisms of apoptosis resistance in stimulated T-cells from T1DM patients.