During infection, naive T cells are activated and differentiated into memory precursor effector cells. Among the effector population, effector T cells that retain CD127 expression can give rise to memory or exhausted T cells based on the infection types. In acute infection, effector cells differentiate into functional memory T cells which produce multiple cytokines, and are able to maintain efficiently via IL-7/IL-5 driven self-renewal. By contrast, exhausted T cells are described in chronic infection with increased expression of inhibitory receptors. They lose the proliferative capacity and function of cytokine production, and might undergo apoptosis.