Dual personality of memory T cells

The generation of protective immunological memory is the basis of effective vaccination. Two distinct types of CD4+ and CD8+ memory T cells have been identified recently: central memory cells present in secondary lymphoid tissues and effector memory cells residing in nonlymphoid tissues. How these subtypes arise and whether they represent distinct lineages are major outstanding questions. Recent reports suggest that cytokines might influence the decision-making process of central versus effector memory, and these data are discussed in the light of our current knowledge.