Co‐expression of TNFR2 and CD25 identifies more of the functional CD4+FOXP3+ regulatory T cells in human peripheral blood

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Abstract
Previously, we found that co‐expression of CD25 and TNFR2 identified the most suppressive subset of mouse Treg. In this study, we report that human peripheral blood (PB) FOXP3+ cells present in CD25high, CD25low and even CD25– subsets of CD4+ cells expressed high levels of TNFR2. Consequently, TNFR2‐expressing CD4+CD25+ Treg included all of the FOXP3+ cells present in the CD4+CD25high subset as well as a substantial proportion of the FOXP3+ cells present in the CD4+CD25low subset. Flow cytometric analysis of PB identified five‐fold more Treg, determined by FOXP3 expression, in the CD4+CD25+TNFR2+ subset than in the CD4+CD25high subset. In addition, similar levels of FOXP3+ cells were identified in both the CD4+CD25+TNFR2+ and CD4+CD25+CD127low/− subsets. Furthermore, the CD4+CD25+TNFR2+ subset expressed high levels of CTLA‐4, CD45RO, CCR4 and low levels of CD45RA and CD127, a phenotype characteristic of Treg. Upon TCR stimulation, human PB CD4+CD25+TNFR2+ cells were anergic and markedly inhibited the proliferation and cytokine production of co‐cultured T‐responder cells. In contrast, CD4+CD25+TNFR2– and CD4+CD25–TNFR2+ T cells did not show inhibitory activity. As some non‐Treg express TNFR2, the combination of CD25 and TNFR2 must be used to identify a larger population of human Treg, a population that may prove to be of diagnostic and therapeutic benefit in cancer and autoimmune diseases.