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. Author manuscript; available in PMC: 2019 Apr 18.
Published in final edited form as: Annu Rev Immunol. 2018 Apr 26;36:411–433. doi: 10.1146/annurev-immunol-042617-053352

Figure 1.

Figure 1

IL-2 biology: IL-2 positively influences the homeostasis and development of a number of T cell lineages. Expression of IL-2R is restricted to nTregs (a) and antigen-activated T cells (b,c), thereby guaranteeing the specificity of IL-2 activities. IL-2-responsive T cell subsets have extremely diverse characteristics and proinflammatory and anti-inflammatory biological roles. Moreover, IL-2 inhibits the differentiation of Th17 and Tfh cells (b), thus making IL-2 an important regulator of T cell lineage commitment. In addition, the levels of IL-2 signaling can define the effector/memory fates of CD4+ and CD8+ T cells: High levels of IL-2 favor the development of short-lived effector cells (b), while low levels of IL-2 signaling promote the differentiation of memory T cells (c). IL-2 stimulation of T cell function is depicted by arrows, IL-2 inhibition of lineage development is represented by inhibitory lines, and no response to IL-2 is indicated by a line with a circle at the end. Abbreviations: IFN-γ, interferon gamma; IL-2R, interleukin-2 receptor; LT-α, lymphotoxin alpha; nTreg, thymically derived regulatory T cell; Tfh, follicular helper T; TNF-α, tumor necrosis factor alpha.