TNF Production or TNFR2 Expression Characterize Distinct States of Regulatory T Cells that Cooperate in Treg Expansion in Cancer and Chronic Inflammation

TNF is a pleiotropic cytokine with immunomodulatory functions mediated by its interaction with the receptor TNFR2, highly expressed by Tregs. However, Tregs can also produce TNF, and an autocrine TNF-TNFR2 loop has been proposed. Here, we describe that both human and mouse Tregs produce TNF in physiological conditions, in several mouse organs, and in mouse models of chronic inflammation and cancer. However, TNF production and TNFR2 expression are differentially distributed: indeed, TNFR2⁺ and TNFR2⁻ Treg subsets are, respectively, poor and strong TNF producers. The two subsets of TNFR2⁺ and TNFR2⁻ Tregs partially maintain their different ability to produce TNF when separately stimulated ex vivo. However, when cocultured, the TNFR2⁺ cells greatly outnumber the TNFR2⁻ counterpart and induce in TNFR2⁻ cells the upregulation of Foxp3 and TNFR2, in association with the transfer of cytoplasmic material. Functionally, TNFR2⁺ Tregs display superior suppressive activity and survival in vitro, both related to an improved resistance to oxidative stress. Overall, our data indicate that Tregs exist in two states, respectively committed to TNF production or TNF sensing through TNFR2, which cooperate in promoting the suppressive function of the whole Treg pool.