Functions of CD8 T-cell subsets secreting different cytokine patterns.

CD8+ T cells can differentiate into two effector phenotypes, Tc1 and Tc2, secreting different cytokine patterns. Both subsets are cytotoxic via the perforin and Fas pathways, and both kill resting and activated B cells, ruling out the possibility of cognate help, although Tc2 cells may provide bystander help. Both subsets induce inflammation with similar cellular infiltrates. Tc1 cytokine synthesis is limited by two mechanisms--IL-4 induces a permanent deficiency in cytokine secretion, and rapid killing of target cells limits CD8+ T-cell activation and cytokine production. These multiple CD8 T-cell activities provide a versatile set of immune functions.