Cutting edge: IL-7-independent regulation of IL-7 receptor alpha expression and memory CD8 T cell development.

Expression of IL-7Ralpha on a subset of Ag-specific effector CD8 T cells is believed to identify memory cell precursors. However, whether IL-7 regulates IL-7Ralpha expression in vivo and is responsible for selective survival of IL-7Ralpha(+) effector cells is unknown. Our results show that in the absence of IL-7, IL-7Ralpha expression was extinguished on the majority of CD8 T cells responding to virus infection, sustained on a subset of effector cells transitioning to memory, and expressed at high levels by memory cells. Additionally, an IL-7-deficient environment was capable of supporting bcl-2 up-regulation and memory cell development in response to virus infection. Thus, IL-7Ralpha regulation occurs independently of IL-7 in responding CD8 T cells, indicating that CD8 memory T cell precursors are not selected by IL-7/IL-7Ralpha interactions.