Christophe Pellefigues

An active resolution is critical to control the duration of inflammation and limit its pathological consequences. Defects in resolution during wound healing allow the emergence of chronic wounds, a common complication in the elderly. Here, we show that basophils accumulate in perivascular areas at the periphery of mouse skin wounds for at least 3 wk, during both the inflammation and resolution phases of wound healing. Depletion of basophils induces an increased secretion of inflammatory molecules, accumulation and activation of pro-inflammatory leukocytes, and delays the wound healing response. Basophils particularly promote epidermal differentiation towards homeostasis. These properties are particularly driven by basophil-derived IL-4. Unexpectedly, aged mice basophils more potently infiltrate skin wounds to promote inflammation resolution. Thus, basophils are pro-resolution cells during an essential biological process such as skin wound healing. Unraveling basophil pro-resolution properties may reveal new strategies to fight chronic wounds in the elderly.

Siam et al. present an interesting new open-access app designed to facilitate the analysis of high-dimensional spectral flow cytometry (SFCM) data. The flow cytometry community definitely needs more good open-access apps to analyze SFCM, especially l...

An active resolution is critical to control the duration of inflammation and limit its pathological consequences. Defects in resolution during wound healing allow the emergence of chronic wounds, a common complication in the elderly. Here, we show that basophils infiltrate the periphery of mouse skin wounds for at least three weeks, during both the inflammation and resolution phases of wound healing. Depletion of basophils induces an increased secretion of inflammatory molecules, accumulation and activation of pro-inflammatory leukocytes, and delays the wound healing response. Basophils particularly promote epidermal differentiation towards homeostasis in the wounds. Basophil-derived IL-4 and M-CSF drive partly their immunoregulatory and healing properties. Unexpectedly, aged mice basophils infiltrate more potently the wounds to promote inflammation resolution, showing a transcriptomic signature biased towards tissue remodeling. Thus, basophils are not pro-inflammatory but pro-resolution cells during an essential biological process such as skin wound healing. Unraveling basophil pro-resolution properties may reveal new strategies to fight chronic wounds in the elderly. SUMMARY The resolution of inflammation is essential for homeostasis and becomes defective with age. Here we show basophil immunoregulatory properties promote resolution during skin wound healing, in both adult and aged mice.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by anti-nuclear autoantibodies whose production is promoted by autoreactive T follicular helper (TFH) cells. During SLE pathogenesis, basophils accumulate in secondary lymphoid organs (SLO), amplify autoantibody production and disease progression through mechanisms that remain to be defined. Here, we provide evidence for a direct functional relationship between TFH cells and basophils during lupus pathogenesis, both in humans and mice. PD-L1 upregulation on basophils and IL-4 production are associated with TFH and TFH2 cell expansions and with disease activity. Pathogenic TFH cell accumulation, maintenance, and function in SLO were dependent on PD-L1 and IL-4 in basophils, which induced a transcriptional program allowing TFH2 cell differentiation and function. Our study establishes a direct mechanistic link between basophils and TFH cells in SLE that promotes autoantibody production and lupus nephritis.

Editorial: The fundamental biology of basophils in health and disease

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibodies raised against nuclear antigens and whose production is promoted by autoreactive T follicular helper (TFH) cells. Basophils, by accumulating in secondary lymphoid organs (SLO), amplify autoantibody production and disease progression through mechanisms to be defined. Here, we demonstrate that a functional relationship between TFH cells and basophils occurs in SLO during lupus pathogenesis. On SLE patient blood basophils, PD-L1 expression was upregulated and associated with TFH and TFH2 cell expansions and with disease activity. In two distinct lupus-like mouse models, TFH cell pathogenic accumulation, maintenance and function, and disease activity were dependent on basophils and their expressions of PD-L1 and IL-4. Our study establishes a direct link between basophils and TFH cells in the SLE context that promotes autoreactive IgG production and lupus nephritis pathogenesis. Altering the basophil/TFH cell axis in the SLE context may represent a promising innovative intervention strategy in SLE.

Systemic lupus erythematosus is a complex autoimmune disease during which patients develop autoantibodies raised against nuclear antigens. During the course of the disease, by accumulating in secondary lymphoid organs (SLOs), basophils support autoreactive plasma cells to amplify autoantibody production. We have recently shown that murine lupus-like disease could be controlled by 10 days of oral treatment with a combination of prostaglandin D₂ (PGD₂) receptor (PTGDR) antagonists through the inhibition of basophil activation and recruitment to SLOs. Importantly, inhibiting solely PTGDR-1 or PTGDR-2 was ineffective, and the development of lupus-like disease could only be dampened by using antagonists for both PTGDR-1 and PTGDR-2. Here, we aimed at establishing a proof of concept that a clinically relevant bispecific antagonist of PTGDR-1 and PTGDR-2 could be efficient to treat murine lupus-like nephritis. Diseased Lyn-deficient female mice received treatment with AMG853 (vidupiprant, a bispecific PTGDR-1/PTGDR-2 antagonist) for 10 days. This led to the dampening of basophil activation and recruitment in SLOs and was associated with a decrease in plasmablast expansion and immunoglobulin E (IgE) production. Ten days of treatment with AMG853 was consequently sufficient in reducing the dsDNA-specific IgG titers, circulating immune complex glomerular deposition, and renal inflammation, which are hallmarks of lupus-like disease. Thus, bispecific PTGDR-1 and PTGDR-2 antagonists, such as AMG853, are a promising class of drugs for the treatment or prevention of organ damage in systemic lupus erythematosus.

Médecine/sciences (M/S), revue internationale dans le domaine de la recherche biologique, médicale et en santé

Background: Mucosal‐associated invariant T (MAIT) cells are unconventional T cells which recognize microbial metabolites presented by the major histocompatibility complex class I‐related molecule MR1. Although MAIT cells have been shown to reside in human and murine skin, their contribution to atopic dermatitis (AD), an inflammatory skin disease associated with barrier dysfunction and microbial translocation, has not yet been determined.Methods: Genetic deletion of MR1 and topical treatment with inhibitory MR1 ligands, which result in the absence and functional inhibition of MAIT cells, respectively, were used to investigate the role of MR1‐dependent immune surveillance in a MC903‐driven murine model of AD.Results: The absence or inhibition of MR1 arrested AD disease progression through the blockade of both eosinophil activation and recruitment of IL‐4‐ and IL‐13‐producing cells. In addition, the therapeutic efficacy of phototherapy against MC903‐driven AD could be increased with prior application of folate, which photodegrades into the inhibitory MR1 ligand 6‐formylpterin.Conclusion: We identified MAIT cells as sentinels and mediators of cutaneous type 2 immunity. Their pathogenic activity can be inhibited by topical application or endogenous generation, via phototherapy, of inhibitory MR1 ligands.