CD40-signalling abrogates induction of RORγt<sup>+</sup> Treg cells by intestinal CD103<sup>+</sup> DCs and causes fatal colitis.

Barthels, Christian; Ogrinc, Ana; Steyer, Verena; Meier, Stefanie; Simon, Ferdinand; Wimmer, Maria; Blutke, Andreas; Straub, Tobias et al. · Nat Commun · 2017

basic_science · Level V

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Abstract

Immune homeostasis in intestinal tissues depends on the generation of regulatory T (Treg) cells. CD103<sup>+</sup> dendritic cells (DCs) acquire microbiota-derived material from the gut lumen for transport to draining lymph nodes and generation of receptor-related orphan γt<sup>+</sup> (RORγt<sup>+</sup>) Helios<sup>-</sup>-induced Treg (iTreg) cells. Here we show CD40-signalling as a microbe-independent signal that can induce migration of CD103<sup>+</sup> DCs from the lamina propria (LP) to the mesenteric lymph nodes. Transgenic mice with constitutive CD11c-specific CD40-signalling have reduced numbers of CD103<sup>+</sup> DCs in LP and a low frequency of RORγt<sup>+</sup>Helios<sup>-</sup> iTreg cells, exacerbated inflammatory Th1/Th17 responses, high titres of microbiota-specific immunoglobulins, dysbiosis and fatal colitis, but no pathology is detected in other tissues. Our data demonstrate a CD40-dependent mechanism capable of abrogating iTreg cell induction by DCs, and suggest that the CD40L/CD40-signalling axis might be able to intervene in the generation of new iTreg cells in order to counter-regulate immune suppression to enhance immunity.

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