Cutting edge:: Memory CD8 T cell maturation occurs independently of CD8αα

As memory CD8 T cells form during acute viral infection, several changes in gene expression and function occur, but little is known about the control of this process. It was reported previously that the homodimer CD8 alpha alpha was involved in generating IL-7R alpha(high) memory CD8 T cell precursors, and consequently, protective memory CD8 T cells did not form in animals significantly impaired in CD8aa expression (E8(I)(-/-) mice). However, the precise contribution of CD8 alpha alpha to sustained IL-7R alpha expression and other memory CD8 T cell-associated changes has not been investigated. We found that IL-7Ra expression and generation of memory CD8 T cells that protect against secondary viral infection was considerably normal in E8(I)(-/-) animals. Interestingly, virus-specific CD4 T cell responses were elevated, and the relative surface levels of CD8 alpha beta in activated T cells were reduced in E8I(-/-) mice compared with wild-type animals. Our results indicate that memory CD8 T cell development can occur independently of CD8 alpha alpha.