CD8A and infection: In contrast to acute/resolved infections where memory CD8 T cell maintenance is antigen-independent but dependent on the homeostatic cytokines IL-7 and IL-15 (Schluns et al., 2000; Wherry and Ahmed, 2004; Surh and Sprent, 2008), maintenance of CD8 T cells during actively replicating chronic infections is strictly dependent on antigen and increased cell turnover (Wherry et al., 2003b; Agnellini et al., 2007).