Prolonged IL-2R alpha expression on virus-specific CD8+ T cells favors terminal effector differentiation in vivo

CD25, the high affinity interleukin-2 (IL-2) receptor alpha-chain, is rapidly upregulated by antigen-specific CD8+ T cells after T cell receptor stimulation. We demonstrated that during an acute viral infection, CD25 expression was dynamic, and a subset of virus-specific CD8+ T cells sustained CD25 expression longer than the rest. Examination of the in vivo fate of effector CD8+ T cells exhibiting differential responsiveness to IL-2 revealed that CD25lo cells, which were relatively less sensitive to IL-2, preferentially upregulated CD127 and CD62L and gave rise to the functional long-lived memory pool. In contrast, CD25hi cells that accumulate enhanced IL-2 signals, proliferated more rapidly, were prone to apoptosis, exhibited a more pronounced effector phenotype, and appeared to be terminally differentiated. Sustained IL-2 receptor signaling resulted in increased CD8+ T cell proliferation, higher granzyme B expression and exaggerated contraction after antigen clearance. These data support the hypothesis that prolonged IL-2 signals during priming promote terminal effector differentiation of CD8+ T cells.

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Kalia V, Sarkar S, Subramaniam S, Haining WN, Smith KA, Ahmed R