Generation and maintenance of memory T cells

Typical immune responses lead to the prominent clonal expansion of antigen- specific T cells followed by their differentiation into effector cells. Mos t effector cells die at the end of the immune response but some of the resp onding cells survive and form long-lived memory cells. The factors controll ing the formation and survival of memory T cells are discussed. Recent evid ence suggests that T memory cells arise from a subset of effector cells. Th e longevity of T memory cells may require continuous contact with cytokines , notably IL-15 for CD8(+) cells.