Selective expression of the interleukin 7 receptor identifies effector CD8 T cells that give rise to long-lived memory cells.

A major unanswered question is what distinguishes the majority of activated CD8 T cells that die after an acute viral infection from the small fraction (5-10%) that survive to become long-lived memory cells. In this study we show that increased expression of the interleukin 7 receptor alpha-chain (IL-7Ralpha) identifies the effector CD8 T cells that will differentiate into memory cells. IL-7R(hi) effector cells contained increased amounts of antiapoptotic molecules, and adoptive transfer of IL-7R(hi) and IL-7R(lo) effector cells showed that IL-7R(hi) cells preferentially gave rise to memory cells that could persist and confer protective immunity. Thus, selective expression of IL-7R identifies memory cell precursors, and this marker may be useful in predicting the number of memory T cells generated after infection or immunization.