Neuropilin-1 is identified as a surface marker to distinguish different Foxp3+ T reg cell subsets under homeostatic conditions.

Although immune checkpoint blockers have yielded significant clinical benefits in patients with different malignancies, the efficacy of these therapies is still limited. Here, we show that disruption of transmembrane protein 176B (TMEM176B) contributes to CD8 + T cell-mediated tumor growth inhibition by unleashing inflammasome activation. Lack of Tmem176b enhances the antitumor activity of anti-CTLA-4 antibodies through mechanisms involving caspase-1/IL-1b activation. Accordingly, patients responding to checkpoint blockade therapies display an activated inflammasome signature. Finally, we identify BayK8644 as a potent TMEM176B inhibitor that promotes CD8 + T cell-mediated tumor control and reinforces the antitumor activity of both anti-CTLA-4 and anti-PD-1 antibodies. Thus, pharmacologic de-repression of the inflammasome by targeting TMEM176B may enhance the therapeutic efficacy of immune checkpoint blockers.

z Both authors contributed equally.x Senior authors.The administration of autologous (recipient-derived) tolerogenic dendritic cells (ATDCs) is under clinical evaluation. However, the molecular mechanisms by which these cells prolong graft survival in a donorspecific manner is unknown. Here, we tested mouse ATDCs for their therapeutic potential in a skin transplantation model. ATDC injection in combination with anti-CD3 treatment induced the accumulation of CD8 þ CD11c þ T cells and significantly prolonged allograft survival. TMEM176B is an intracellular protein expressed in ATDCs and initially identified in allograft tolerance. We show that Tmem176b À/À ATDCs completely failed to trigger both phenomena but recovered their effect when loaded with donor peptides before injection. These results strongly suggested that ATDCs require TMEM176B to crosspresent antigens in a tolerogenic fashion. In agreement with this, Tmem176b À/À ATDCs specifically failed to cross-present male antigens or ovalbumin to CD8 þ T cells. Finally, we observed that a Tmem176b-dependent cation current controls phagosomal pH, a critical parameter in cross-presentation. Thus, ATDCs require TMEM176B to cross-present donor antigens to induce donor-specific CD8 þ CD11c þ T cells with regulatory properties and prolong graft survival.

We identified a novel rat gene specifically overexpressed in tolerated heart allografts in a model of tolerance induced by donor-specific blood transfusion (DST). We named this gene TORID, for tolerancerelated and induced transcript. We show that TORID expression can be attributed to non-T cells infiltrating tolerated grafts. Interestingly, TORID overexpression was also observed in long-term grafts from a different model of tolerance in which chronic rejection does not occur. Comparison of the predicted amino acid sequence of TORID and of its human counterpart LR8 showed an homology with the four-transmembrane CD20/FceRIb family proteins. We investigated TORID expression in naive rat immune cells and lymphoid tissues. TORID was found to be preferentially expressed in cells of the myeloid lineage such as macrophages and dendritic cells (DCs). Its expression dramatically decreased following activation/maturation. Similar results were obtained in human monocyte-derived DCs. Interestingly, TORID overexpression in bone marrowderived DCs alters expression of MHC II and CD86 and production of IL12p40 following activation. These results suggest that TORID may be involved in the control of DC maturation and may, therefore, play a role in the induction or maintenance of allograft tolerance.

We have identified in the rat a new subset of MHC class II+ CD4+CD3−CD11b− leukocytes that produce high amounts of type I IFN upon viral stimulation and that appeared homologous to plasmacytoid DC (pDC) previously described in humans and mice. These cells exhibited the following phenotype: CD5+,CD90+,CD45R+,CD45RC+,CD11c−,CD161a+,CD200+,CD172a+,CD32+,CD86+. Rat pDC did not express the DC-specific marker OX62 and were more abundant in the spleen than the classical CD4+ and CD4− subsets of OX62+CD11b+ DC we previously described that produced very little, if any, type I IFN. Spleen pDC exhibited an undifferentiated morphology and rapidly died in vitro, but showed extensive dendrite formation, survival, maturation, and moderate type I IFN production upon stimulation by oligonucleotides containing type B CpG motifs (CpG ODN). Type A CpG ODN and CD40 ligand induced pDC to produce large amounts of type I IFN, but did not promote maturation. CpG ODN and CD40 ligand, but not influenza virus, induced IL-12p40 and IL-6 secretion. Spleen pDC did not produce IL-12p70, TNF-α, IL-1β, or IL-10 using these stimulation conditions. Correlating with their strong responsiveness to virus and CpG ODN, rat pDC specifically expressed Toll-like receptor 7 and 9 mRNA. Fresh spleen pDC were poor stimulators of allogenic CD4+ and CD8+ T cells, but became potent inducers of allogenic T cell proliferation as well as Th1 differentiation after stimulation by type B CpG. Therefore, rat pDC appear very similar to human pDC, indicating that the specific phenotype and functions of pDC have been highly conserved between species.

Retinoid-related orphan receptor gamma t (RORγt) is a master transcription factor central to type 17 immunity involving cells such as T helper 17, group 3 innate lymphoid cells or IL-17-producing γδ T cells. Here we show that the intracellular ion channel TMEM176B and its homologue TMEM176A are strongly expressed in these RORγt+ cells. We demonstrate that TMEM176A and B exhibit a similar cation channel activity and mainly colocalise in close proximity to the trans-Golgi network. Strikingly, in the mouse, the loss of Tmem176b is systematically associated with a strong upregulation of Tmem176a. While Tmem176b single-deficiency has no effect on the course of experimental autoimmune encephalomyelitis, T cell or DSS-induced colitis, it significantly reduces imiquimod-induced psoriasis-like skin inflammation. These findings shed light on a potentially novel specific process linked to post-Golgi trafficking for modulating the function of RORγt+ cells and indicate that both homologues should be simultaneously targeted to clearly elucidate the role of this intracellular ion flow.

Innovative therapeutic strategies are needed to diminish the impact of harmful immunosuppression in transplantation. Dendritic cell (DC)-based therapy is a promising approach for induction of antigenspecific tolerance. Using a heart allograft model in rats, we analyzed the immunoregulatory mechanisms by which injection of autologous tolerogenic DCs (ATDCs) plus suboptimal immunosuppression promotes indefinite graft survival. Surprisingly, we determined that Interferon-gamma (IFNG), a cytokine expected to be propathogenic, was threefold increased in the spleen of tolerant rats.

No abstract