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Background: Pathogenesis of atopic dermatitis (AD) involves interaction between type 2 cells that include basophils, mast cells, innate lymphoid type 2 cells (ILC2), and Th2 cells. Levels of IL-4 and IL-13 are elevated in AD patients. Objective: Here, we investigated the distribution of type 2 cells and the source of IL-4 and IL-13 in skin and blood of AD relative to psoriasis. Methods: Lesional skin biopsies and blood were collected from patients. Skin cell suspensions were prepared by mild enzymatic digestion and mechanical dissociation. IL-4 and IL-13 expression was analyzed at single-cell level before or after stimulation using flow cytometry. Results: Frequencies of basophils, ILC2 and Th2 but not mast cells were significantly elevated in skin, and not blood, of AD relative to psoriasis. IL-4 production by circulating basophils and Th2 cells, and IL-13 by ILCs and Th2 cells was similar in both diseases. In contrast, skin T cells expressed IL-4 and IL-13 prior to stimulation in AD when compared to psoriasis. Moreover, skin basophils, which were detected in AD only, expressed IL-4 following stimulation. Interestingly, basophils and ILC2 were positively correlated in skin, whereas skin basophils were inversely correlated with blood ILC2. Conclusions: Lesional AD skin harbors a distinctive innate and adaptive type 2 profile, which is characterized by basophils producing IL-4, Th2 cells expressing IL-4 or IL-13, and ILC2. This underlies the therapeutic efficacy of targeting IL-4 and IL-13 signaling pathways in AD.

The drug targets IL23 and IL12 regulate pathogenicity and plasticity of intestinal Th17 cells in Crohn's disease (CD) and ulcerative colitis (UC), the two most common inflammatory bowel diseases (IBD). However, studies examining Th17 dysregulation in mesenteric lymph nodes (mLNs) of these patients are rare. We showed that in mLNs, CD could be distinguished from UC by increased frequencies of CCR6 + CXCR3 − RORγ + Tbet − CD4 + (Th17) memory T cells enriched in CD62L low effector memory T cells (T EM ), and their differentially expressed molecular profile. Th17 T EM cells (expressing IL17A, IL17F, RORC , and STAT3 ) displayed a higher pathogenic/cytotoxic ( IL23R, IL18RAP , and GZMB, CD160, PRF1 ) gene signature in CD relative to UC, while non-pathogenic/regulatory genes ( IL9, FOXP3, CTLA4 ) were more elevated in UC. In both CD and UC, IL12 but not IL23, augmented IFNγ expression in Th17 T EM and switched their molecular profile toward an ex-Th17 (Th1 * )-biased transcriptomic signature (increased IFNG , and decreased TCF7, IL17A ), suggesting that Th17 plasticity occurs in mLNs before their recruitment to inflamed colon. We propose that differences observed between Th17 cell frequencies and their molecular profile in CD and UC might have implications in understanding disease pathogenesis, and thus, therapeutic management of patients with IBD.

Patients with systemic sclerosis (SSc) display altered intestinal microbiota. However, the influence of intestinal dysbiosis on the development of experimental SSc remains unknown. Topoisomerase I peptide-loaded dendritic cell immunization induces SSc-like disease, with progressive skin and lung fibrosis. Breeders were given streptomycin and pups continued to receive antibiotic (ATB) until endpoint (lifelongATB). Alternately, ATB was withdrawn (earlyATB) or initiated (adultATB) during adulthood. Topoisomerase I peptide-loaded dendritic cell (no ATB) immunization induced pronounced skin fibrosis, with increased matrix (Col1a1), profibrotic (Il13, Tweakr), and vascular function (Serpine1) gene expression. Remarkably, earlyATB exposure was sufficient to augment skin Col5a1 and Il13 expression, and inflammatory cell infiltration, which included IL-13 cells, mononuclear phagocytes, and mast cells. Moreover, skin pathology exacerbation was also observed in lifelongATB and adultATB groups. Oral streptomycin administration induced intestinal dysbiosis, with exposure limited to early life (earlyATB) being sufficient to cause long-term modification of the microbiota and a shift toward increased Bacteroidetes/Firmicutes ratio. Finally, aggravated lung fibrosis and dysregulated pulmonary T-cell responses were observed in earlyATB and lifelongATB but not adultATB-exposed mice. Collectively, intestinal microbiota manipulation with streptomycin exacerbated pathology in two distinct sites, skin and lungs, with early life being a critical window to affect the course of SSc-like disease.

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