IL-15Rα expression on CD8+ T cells is dispensable for T cell memory

The generation and maintenance of immunological memory requires the activation, expansion, and persistent proliferation of antigen-specific T cells. Recent work suggests that IL-15 may be important for this process. Surprisingly, we now find that expression of the high-affinity receptor for IL-15, IL-15Ralpha, on T cells is dispensable for the generation or maintenance of memory CD8(+) T cells. By contrast, IL-15Ralpha expression on cells other than T cells is absolutely critical for this function. These findings may be related to IL-15Ralpha's ability to present IL-15 in trans to low-affinity IL-15Rbeta/gamma(c) receptors on memory CD8(+) T cells. These unexpected results provide insights into how IL-15Ralpha supports memory CD8(+) T cells.