Estrada Brull, A. | Search bioRxiv

bioRxiv2026

IL-12R signaling promotes type 1 regulatory T cell specialization by sustaining T-bet

Elucidating how regulatory T (Treg) cells specialize and acquire specific suppressive capacities is key for understanding immune regulation in autoimmunity and cancer. Although IL-12 is a key driver of Th1 differentiation, its role in Treg cells remains poorly defined. Here, we investigated whether IL-12R signaling contributes to Treg cell specialization during Th1 immune responses. We show that IL-12R{beta}2 KO Treg cells display reduced type 1 specialization following LCMV infection, resulting in impaired suppressive capacity. Mechanistically, IFN-{gamma} induces a first peak of T-bet, whereas IL-12 acts downstream to sustain T-bet through a positive feedback loop. The decreased suppressive function of IL-12R{beta}2 KO Treg cells alters effector T cell responses during both acute and chronic infections. Importantly, human Treg cells also respond to IL-12, promoting enhanced type 1 specialization. Together, these findings establish IL-12 as a critical regulator of type 1 Treg specialization and highlight the therapeutic potential of targeting this pathway. TeaserIL-12R signaling in Treg cells enables sustained T-bet expression, programing type 1 Tregs for suppression of Th1 responses.

immunology↗

bioRxiv2022

Microbiota colonization tunes the antigen threshold of microbiota-specific T cell activation in the gut

Harnessing the potential of commensal bacteria for immunomodulatory therapy in the gut requires the identification of conditions that modulate immune activation towards incoming colonizing bacteria. In this study, we used the commensal Bacteroides thetaiotaomicron (B.theta) and combined it with B.theta-specific transgenic T cells, in the context of defined colonization of gnotobiotic and immunodeficiency mouse models, to probe the factors modulating bacteria-specific T cell activation against newly colonizing bacteria. After colonizing germ-free (GF) and conventionally raised (SPF) mice with B.theta, we only observed proliferation of B.theta-specific T cells in GF mice. Using simple gnotobiotic communities we could further demonstrate that T-cell activation against newly colonizing gut bacteria is restricted by previous bacteria colonization in GF mice. However, this restriction requires a functional adaptive immune system as Rag1-/- allowed B.theta-specific T cell proliferation even after previous colonization. Interestingly, this phenomenon seems to be dependent on the type of TCR-transgenic model used. B.theta-specific transgenic T cells also proliferated after gut colonization with an E.coli strain carrying the B.theta-specific epitope. However, this was not the case for the SM-1 transgenic T cells as they did not proliferate after similar gut colonization with an E.coli strain expressing the cognate epitope. In summary, we found that activation of T cells towards incoming bacteria in the gut is modulated by the influence of colonizing bacteria on the adaptive immune system of the host.

immunology↗