Succinate acts as an extracellular mediator signaling through the G protein-coupled receptor GPR91. Here we show that dendritic cells had high expression of GPR91. In these cells, succinate triggered intracellular calcium mobilization, induced migratory responses and acted in synergy with Toll-like receptor ligands for the production of proinflammatory cytokines. Succinate also enhanced antigen-specific activation of human and mouse helper T cells. GPR91-deficient mice had less migration of Langerhans cells to draining lymph nodes and impaired tetanus toxoid-specific recall T cell responses. Furthermore, GPR91-deficient allografts elicited weaker transplant rejection than did the corresponding grafts from wild-type mice. Our results suggest that the succinate receptor GPR91 is involved in sensing immunological danger, which establishes a link between immunity and a metabolite of cellular respiration.

CCR7-mediated migration of naive T cells into the secondary lymphoid organs is a prerequisite for their encounter with mature dendritic cells, the productive presentation of cognate antigen, and consequent T cell proliferation and effector differentiation. Therefore, CCR7 was suggested to play an important role in the initiation of adaptive immune responses. In this study, we show that primary immunity can also develop in the absence of CCR7. Moreover, CCR7-deficient knockout (KO) mice display augmented immune responses. Our data cumulatively suggest that enhanced immunity in CCR7 KO mice is caused by the defective lymph node (LN) positioning of FoxP3+ CD4+ CD25+ regulatory T cells (T reg cells) and the consequent impediment of their function. The FoxP3+ T reg cells express CCR7 and, after their adoptive transfer, migrate into the LNs of wild-type mice. Here, they proliferate in situ upon antigen stimulation and inhibit the generation of antigen-specific T cells. Conversely, transferred CCR7-deficient T reg cells fail to migrate into the LNs and suppress antigen-induced T cell responses. The transfer of combinations of naive and T reg cells from wild-type and CCR7 KO mice into syngeneic severe combined immunodeficient mice directly demonstrates that CCR7-deficient T reg cells are less effective than their wild-type counterparts in preventing the development of inflammatory bowel disease.

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There is a need for safe and effective therapies for inflammatory skin diseases. Current topical and systemic treatment of psoriasis is effective but suffers from side-effects or is inconvenient. The therapeutic armamentarium for atopic dermatitis is very limited and far from satisfactory. In vivo preclinical data are presented for SDZ ASM 981, a novel ascomycin macrolactam derivative with high anti-inflammatory activity. Anti-inflammatory activity was observed in mouse, rat and pig models of allergic contact dermatitis. In the pig model, topical SDZ ASM 981 was as effective as the ultrapotent corticosteroid clobetasol-17-propionate, and when compared with a series of commercial topical corticosteroid preparations, 0.1% SDZ ASM 981 had equivalent efficacy to clobetasol-17-propionate (0.05%), the most potent product on the market. Unlike the corticosteroid, however, SDZ ASM 981 did not cause skin atrophy in pigs. SDZ ASM 981 potently inhibited allergic contact dermatitis in mice and rats when given systemically, and oral treatment was more effective than cyclosporin A in rats. Furthermore, SDZ ASM 981 has a low potential for affecting systemic immune responses, as demonstrated in rat models of localized graft vs. host reaction and allogeneic kidney transplantation. Preclinical results suggest that SDZ ASM 981 has the potential to be a well-tolerated and effective drug for topical as well as oral treatment of inflammatory skin diseases.

PKC isoforms t, α, and β play fundamental roles in the activation of T cells and other immune cell functions.Here we show that the PKC inhibitor AEB071 both abolishes the production of several cytokines by activated human T cells, keratinocytes, and macrophages in vitro and inhibits an acute allergic contact dermatitis response in rats. To translate these findings into humans, single and multiple ascending oral doses of AEB071 were administered to healthy volunteers and patients with psoriasis, respectively. AEB071 was well tolerated with no clinically relevant laboratory abnormalities. Ex vivo stimulation of lymphocytes from subjects exposed to single doses of AEB071 resulted in a dose-dependent inhibition of both lymphocyte proliferation and IL2 mRNA expression. Clinical severity of psoriasis was reduced up to 69% compared with baseline after 2 weeks of treatment, as measured by the Psoriasis Area Severity Index (PASI) score. The improvement in psoriasis patients was accompanied by histological improvement of skin lesions and may be partially explained by a substantial reduction of p40 + dermal cells, which are known to mediate psoriasis. These data suggest that AEB071 could be an effective novel treatment regimen for psoriasis and other autoimmune diseases, and that AEB071 warrants long-term studies to establish safety and efficacy.