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Cutaneous B-cell lymphomas (CBL) comprise a diverse group of diseases with variable clinical course and prognosis. The cellular and molecular mechanisms underlying the pathogenesis of CBL remain ill-defined. Here we performed single-cell RNA sequencing combined with B-cell and T-cell receptor sequencing in three distinct CBL entities. In contrast to benign cutaneous pseudolymphomas and healthy skin, each CBL variant contained a single dominant B-cell clone. In marginal zone lymphoproliferative disorder (MZLPD), expanded clones generally showed terminal differentiation along a physiological trajectory towards plasma cells and displayed transcriptomic profiles indistinguishable from the benign polyclonal bystander B-cells. Follicle center lymphoma (FCL) clones also exhibited a canonical B-cell marker profile but consisted of more homogeneous populations of proliferating and nonproliferating germinal center (GC) B-cell-like phenotypes. In the most aggressive CBL, diffuse large B-cell lymphoma, leg type (DCBCL-LT), cells revealed multiple non-physiological marker profiles as well as aberrant proliferative activity beyond conventional GC-like cells. Fibroblasts in MZLPD, FCL and pseudolymphomas, but not DLBCL-LT, expressed the classical chemotactic chemokineCXCL13. These data suggest that in cutaneous B-cell disorders other than DLBCL-LT, physiological immune circuits are primarily operative, consistent with their overall indolent behavior.Key PointsThis is the first comprehensive molecular map of primary cutaneous B-cell lymphoproliferative disorders.Differences between entities were primarily geared by the expanded B-cell clone and less by other immune or stromal cells.

Therapeutic options for autoimmune diseases typically consist of broad and targeted immunosuppressive agents. However, sustained clinical benefit is rarely achieved, as the disease phenotype usually returns after cessation of treatment. To better understand tissue-resident immune memory in human disease, we investigated patients with atopic dermatitis (AD) who underwent short-term or long-term treatment with the IL-4Rα blocker dupilumab. Using multi-omics profiling with single-cell RNA sequencing and multiplex proteomics, we found significant decreases in overall skin immune cell counts and normalization of transcriptomic dysregulation in keratinocytes consistent with clearance of disease. However, we identified specific immune cell populations that persisted for up to a year after clinical remission while being absent from healthy controls. These populations included LAMP3+CCL22+ mature dendritic cells, CRTH2+CD161+ T helper (“TH2A”) cells, and CRTAM+ cytotoxic T cells, which expressed high levels of CCL17 (dendritic cells) and IL13 (T cells). TH2A cells showed a characteristic cytokine receptor constellation with IL17RB, IL1RL1 (ST2), and CRLF2 expression, suggesting that these cells are key responders to the AD-typical epidermal alarmins IL-25, IL-33, and TSLP, respectively. We thus identified disease-linked immune cell populations in resolved AD indicative of a persisting disease memory, facilitating a rapid response system of epidermal-dermal cross-talk between keratinocytes, dendritic cells, and T cells. This observation may help to explain the disease recurrence upon termination of immunosuppressive treatments in AD, and it identifies potential disease memory–linked cell types that may be targeted to achieve a more sustained therapeutic response.

Therapeutic options for autoimmune diseases typically consist of broad and targeted immunosuppressive agents. However, sustained clinical benefit is rarely achieved, as the disease phenotype usually returns after cessation of treatment. To better understand tissue-resident immune memory in human disease, we investigated patients with atopic dermatitis (AD) who underwent short-term or long-term treatment with the IL-4Rα blocker dupilumab. Using multi-omics profiling with single-cell RNA sequencing and multiplex proteomics, we found significant decreases in overall skin immune cell counts and normalization of transcriptomic dysregulation in keratinocytes consistent with clearance of disease. However, we identified specific immune cell populations that persisted for up to a year after clinical remission while being absent from healthy controls. These populations included

Background Atopic dermatitis (AD) is the most common chronic inflammatory skin disease, but its complex pathogenesis is only insufficiently understood, resulting in still limited treatment options. Objective We sought to characterize AD on both transcriptomic and proteomic levels in humans. Methods We used skin suction blistering, a painless and nonscarring procedure that can simultaneously sample skin cells and interstitial fluid. We then compared results with conventional biopsies. Results Suction blistering captured epidermal and most immune cells equally well as biopsies, except for mast cells and nonmigratory CD163+ macrophages that were only present in biopsy isolates. Using single-cell RNA sequencing, we found comparable transcriptional profiles of key inflammatory pathways between blister and biopsy AD, but suction blistering was superior in cell-specific resolution for high-abundance transcripts (KRT1/KRT10, KRT16/KRT6A, S100A8/S100A9), which showed some background signals in biopsy isolates. Compared with healthy controls, we found characteristic upregulation of AD-typical cytokines such as IL13 and IL22 in Th2 and Th22 cells, respectively, but we also discovered these mediators in proliferating T cells and natural killer T cells, that also expressed the antimicrobial cytokine IL26. Overall, not T cells, but myeloid cells were most strongly enriched in AD, and we found dendritic cell (CLEC7A, amphiregulin/AREG, EREG) and macrophage products (CCL13) among the top upregulated proteins in AD blister fluid proteomic analyses. Conclusion These data show that by using cutting-edge technology, suction blistering offers several advantages over conventional biopsies, including better transcriptomic resolution of skin cells, combined with proteomic information from interstitial fluid, unraveling novel inflammatory players that shape the cellular and proteomic microenvironment of AD.