Influence of TGFbeta on human resting CD4+ T cells

Based on studies in knockout mice, several inhibitory factors such as TGF-beta, IL-10, or CTLA-4 have been implicated as gate keepers of adaptive immune responses. Lack of these inhibitory molecules leads to massive inflammatory responses mainly mediated by activated T cells. In humans, the integration of these inhibitory signals for keeping T cells at a resting state is less well understood. To elucidate this regulatory network we assessed early genome-wide transcriptional changes during serum deprivation in human mature CD4+ T cells. The most striking observation was a "TGF-beta loss signature" defined by downregulation of many known TGF-beta target genes. Moreover, numerous novel TGF-beta target genes were identified that are under the suppressive control of TGF-beta. Expression of these genes was upregulated once TGF-beta signaling was lost during serum deprivation and again suppressed upon TGF-beta reconstitution. Constitutive TGF-beta signaling was corroborated by demonstrating phosphorylated SMAD2/3 in resting human CD4+ T cells in situ, which were dephosphorylated during serum deprivation and re-phosphorylated by minute amounts of TGF-beta. Loss of TGF-beta signaling was particularly important for T cell proliferation induced by low-level T cell receptor and costimulatory signals. We suggest TGF-beta to be the most prominent factor actively keeping human CD4+ T cells at a resting state.

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Classen S, Zander T, Eggle D, Chemnitz JM, Brors B, Büchmann I, Popov A, Beyer M, Eils R, Debey S, Schultze JL