Differential role of IL‐2R signaling for CD8+ T cell responses in acute and chronic viral infections

AbstractIL‐2 is a cytokine with multiple and even divergent functions; it has been described as a key cytokine for in vitro T cell proliferation but is also essential for down‐regulating T cell responses by inducing activation‐induced cell death as well as regulatory T cells. The in vivo analysis of IL‐2 function in regulating specific T cell responses has been hampered by the fact that mice deficient in IL‐2 or its receptors develop lymphoproliferative diseases and/or autoimmunity. Here we generated chimeric mice harboring both IL‐2R‐competent and IL‐2R‐deficient T cells and assessed CD8+ T cell induction, function and maintenance after acute or persistent viral infections. Induction and maintenance of CD8+ T cells were relatively independent of IL‐2R signaling during acute/resolved viral infection. In marked contrast, IL‐2 was crucial for secondary expansion of memory CD8+ T cells and for the maintenance of virus‐specific CD8+ T cells during persistent viral infections. Thus, depending on the chronicity of antigen exposure, IL‐2R signaling is either essential or largely dispensable for induction and maintenance of virus‐specific CD8+ T cell responses.