Distinct kinetics of cytokine production and cytolysis in effector and memory T cells after viral infection

In the present study, naive T cells were compared with in vivo generated ef fector and memory T cells expressing the same TCR specific for lymphocytic choriomeningitis virus. Upon restimulation in vitro, the same minimal conce ntrations of the full agonist peptide p33 and also of weak and partial agon ist peptides were required for proliferation of naive, effector and memory T cells, indicating no difference in threshold of activation. However, acti vation kinetics were distinct. While effector cytotoxic T cells exhibited i mmediate ex vivo lytic effector function, naive and memory T cells required 12 h and more exposure to antigen to develop lytic activity. However, both effector and memory T cells contained IFN-gamma mRNA in vivo and required less than 3 h for secretion of cytokines upon restimulation in vitro. In co ntrast, naive T cells did not contain IFN-gamma mRNA and required more than 12 h for cytokine secretion. Our results show that memory T cells exhibit a unique phenotype in that they produce cytokines and commit to proliferati on as rapidly as effector cells, whereas they resemble naive T cells in the time requirement for development of cytolytic function.