Regulatory T (Treg) cells induce immunologic tolerance by suppressing effector functions of conventional lymphocytes in the periphery. On the other hand, immune silencing is mediated by recognition of phosphatidylserine (PS) on apoptotic cells by phagocytes. Here we describe expression of the PS‐binding protein Annexin V (ANXA5) in CD4⁺ CD25^hi Treg cells at the mRNA and protein levels. CD4⁺ ANXA5⁺ T cells constitute about 0·1%–0·6% of peripheral blood CD3⁺ T cells, exhibit co‐expression of several Treg markers, such as Forkhead box P3, programmed cell death protein‐1, cytotoxic T‐lymphocyte antigen‐4 and CD38. In vitro, ANXA5⁺ Treg cells showed enhanced adhesion to PS⁺ endothelial cells. Stimulated by anti‐CD3 and PS⁺ syngeneic antigen‐presenting cells CD4⁺ ANXA5⁺ T cells expanded in the absence of exogenous interleukin‐2. CD4⁺ ANXA5⁺ T cells suppressed CD4⁺ ANXA5⁻ T‐cell proliferation and mammalian target of rapamycin phosphorylation, partially dependent on cell contact. CD4⁺ ANXA5⁺ T‐cell‐mediated suppression was allo‐specific and accompanied by an increased production of anti‐inflammatory mediators. In vivo, using a model of delayed type hypersensitivity, murine CD4⁺ ANXA5⁺ T cells inhibited T helper type 1 responses. In conclusion, we report for the first time expression of ANXA5 on a subset of Treg cells that might bridge classical regulatory Treg function with immune silencing.

(1) Background: Autoimmune pancreatitis (AIP) is mainly treated with steroids. Using an AIP mouse model, we investigated two potential alternatives, the transforming growth factor-β-activated kinase 1 inhibitor, takinib, and the Janus kinase inhibitor, tofacitinib. (2) Methods: In a multicenter preclinical study, MRL/MpJ mice were injected with polyinosinic/polycytidylic acid (poly I:C) for two weeks to induce AIP. They were then treated for four weeks with either takinib (25, 50, or 75 mg/kg body weight), tofacitinib (5, 10 or 15 mg/kg), dexamethasone (1 mg/kg), or solvent, while the poly I:C injections were continued. The severity of AIP was assessed histopathologically. Flow cytometry was used to examine lymphocyte subtypes in the spleen and mesenteric lymph nodes. The pancreatic gene expression profiles were analyzed by RNA sequencing. (3) Results: Poly I:C-treated mice developed severe AIP with inflammation, destruction of acinar tissue, and fibrosis. Dexamethasone significantly attenuated the disease, while takinib or tofacitinib had no effects. Dexamethasone also antagonized the effects of poly I:C on the relative frequencies of the AIP-associated lymphocyte subtypes CD4/CD69, CD8/CD44^high, and CD4/CD25/FoxP3 in the spleen. In the principal component analysis of pancreatic transcriptomics, poly I:C-injected mice treated with tofacitinib, takinib, or solvent clustered together, while untreated and dexamethasone-treated mice formed separate, unique clusters. (4) Conclusions: Dexamethasone effectively reduced AIP severity, while takinib and tofacitinib were ineffective. The unique gene expression profile in dexamethasone-treated mice may provide a basis for identifying new drug targets for AIP treatment.

Psoriasis is a chronic inflammatory skin condition. Repeated epicutaneous application of Aldara® (imiquimod) cream results in psoriasiform dermatitis in mice. The Aldara®‐induced psoriasiform dermatitis (AIPD) mouse model has been used to examine the pathogenesis of psoriasis. Here, we used a forward genetics approach in which we compared AIPD that developed in 13 different inbred mouse strains to identify genes and pathways that modulated disease severity. Among our primary results, we found that the severity of AIPD differed substantially between different strains of inbred mice and that these variations were associated with polymorphisms in Itga11. The Itga11 gene encodes the integrin α11 subunit that heterodimerizes with the integrin β1 subunit to form integrin α11β1. Less information is available about the function of ITGA11 in skin inflammation; however, a role in the regulation of cutaneous wound healing, specifically the development of dermal fibrosis, has been described. Experiments performed with Itga11 gene‐deleted (Itga11^−/−) mice revealed that the integrin α11 subunit contributes substantially to the clinical phenotype as well as the histopathological and molecular findings associated with skin inflammation characteristic of AIPD. Although the skin transcriptomes of Itga11^−/− and WT mice do not differ from one another under physiological conditions, distinct transcriptomes emerge in these strains in response to the induction of AIPD. Most of the differentially expressed genes contributed to extracellular matrix organization, immune system, and metabolism of lipids pathways. Consistent with these findings, we detected a reduced number of fibroblasts and inflammatory cells, including macrophages, T cells, and tissue‐resident memory T cells in skin samples from Itga11^−/− mice in response to AIPD induction. Collectively, our results reveal that Itga11 plays a critical role in promoting skin inflammation in AIPD and thus might be targeted for the development of novel therapeutics for psoriasiform skin conditions. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.