UNEQUAL DEATH IN T-HELPER CELL (TH)1 AND TH2 EFFECTORS - TH1, BUT NOTTH2, EFFECTORS UNDERGO RAPID FAS FASL-MEDIATED APOPTOSIS/

T helper cell (Th) 1, but not Th2, effectors undergo rapid Fas/Fas lig and (FasL)-mediated, activation-induced cell death upon restimulation with antigen. Unequal apoptosis is also observed without restimulation , after a longer lag period. Both effectors undergo delayed apoptosis induced by a non-Fas-mediated pathway. When Th1 and Th2 effectors are co-cultured, Th2 effectors survive preferentially, suggesting the resp onsible factor(s) is intrinsic to each population. Both Th1 and Th2 ef fectors express Fas and Fast, but only Th2 effectors express high leve ls of FAP-1, a Fas-associated phosphatase that may act to inhibit Fas signaling. The rapid death of Th1 effecters leading to selective Th2 s urvival provides a novel mechanism for differential regulation of the two subsets.