CD8Tc1 and Tc2 cells secrete distinct cytokine patterns in vitro and in vivo but induce similar inflammatory reactions.

Naive CD8 T cells, similar to CD4 T cells, can differentiate into at least two subsets of cytolytic effector cells with distinct cytokine patterns: T cytotoxic-1 (Tc1) cells secrete a Th1-like cytokine pattern, including IL-2 and IFN-gamma; and Tc2 cells produce Th2 cytokines, including IL-4, IL-5, and IL-10. As CD4 Th1 cells induce delayed-type hypersensitivity (DTH) more effectively than Th2 cells, we tested the potential ability of Tc1 and Tc2 cells to induce DTH. Allospecific Tc1 or Tc2 cells were injected into the footpads of naive mice expressing the target Ag. Tc1 and Tc2 cells induced comparable levels of Ag-specific footpad swelling with similar kinetics. They also induced similar levels of footpad edema and similar infiltration of macrophages and neutrophils. However, Tc2 cells induced slightly more eosinophil infiltration. Analysis of footpad extracts showed that Tc1 and Tc2 cells retained their distinct in vitro cytokine profiles in the injected footpads. These results suggest that both Tc1 and Tc2 cytokines can be associated with the DTH reaction induced by CD8 T cells. Perforin-deficient Tc1 or Tc2 cells also induced DTH, although at lower levels, suggesting that perforin-mediated cytotoxicity of CD8 T cells is not essential for CD8-induced DTH. Thus, despite their distinct cytokine profiles in vitro and in vivo, Tc1 and Tc2 cells induce similar DTH reactions.