Specifically, PD1 expression correlated with positive T cell function or activation markers such as 4-1BB in breast cancer and CD38 in HIV (14, 15, 32); the differentiation marker CD127 and not “exhaustion markers” correlated with positive prognosis in HCV infection (16); CD127 levels also correlated with PD1, 2B4, CD160, and KLRG1 expression in HCV infection (33); TIM3 expression correlated with effector memory phenotype in active tuberculosis (34), or questions were raised regarding PD1 as “exhaustion” marker in SIV infection depending on whether total or memory T cell were considered (35). The gene discussed is HAVCR2; the disease is tuberculosis.