Cutting edge: OFF cycling of TNF production by antigen-specific CD8(+) T cells is antigen independent

Although they are known for their capacity to kill infected cells, Ag-speci fic CD8(+) T cells elaborate other effector mechanisms, including TNF and I FN-gamma, that contribute to defense against infection, Ag-specific CD8(+) T cells rapidly turn ON and turn OFF IFN-gamma production in direct respons e to Ag contact, presumably to minimize the potential immunopathology that could result from inappropriate secretion of this inflammatory mediator. In this study, we show, using in vitro propagated and directly ex vivo-analyz ed Ag-specific CD8(+) T cells, that in contrast to Ag-dependent ON/OFF cycl ing of IFN-gamma production, the cessation of TNF production by the same IF N-gamma producing cells is rapid and Ag independent.