This in vitro IFN-γ unresponsiveness of the vast majority of these highly activated effector CD8 T cells is somewhat reminiscent of the T cell exhaustion seen under conditions of prolonged antigenic stimulus in chronic viral infections and closely resembles the “stunned” phenotype reported in the febrile phase of other acute infections, such as HIV infection and viral hepatitis (36, 37). Here, IFNG is linked to animal viral hepatitis.