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Psoriasis is a recurrent, chronic, immune-mediated, systemic inflammatory disease of the skin, joints, and other organic systems. After atopic dermatitis, chronic stationary psoriasis is the most common inflammatory skin disease, affecting an average of 2–4% of the world's population. The disease carries a significant burden due to its numerous comorbidities and the major impact on patients' social and emotional aspects of life. According to current knowledge, psoriasis is a multifactorial disease that occurs in genetically predisposed individuals under various environmental factors, which trigger an immune response disorder with a series of complex inflammatory cascades. The disease is initiated and maintained by mutual interaction of the innate and adaptive immune cells, primarily dendritic cells, T lymphocytes, and keratinocytes, whose leading role alternates at different stages of the disease, consisting mainly in the IL-23/Th17 pathway. Inflammatory events result in consequent epidermal and dermal changes and evolution of the characteristic psoriatic phenotype, respectively. This paper aims to present a comprehensive overview of current knowledge on psoriasis genetic and environmental etiological factors, immunopathogenesis, and the leading cellular and cytokine participants in the inflammatory pathways of this disease. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) is the most common chronic inflammatory skin disease with complex pathogenesis for which the cellular and molecular crosstalk in AD skin has not been fully understood. Methods: Skin tissues examined for spatial gene expression were derived from the upper arm of 6 healthy control (HC) donors and 7 AD patients (lesion and nonlesion). We performed spatial transcriptomics sequencing to characterize the cellular infiltrate in lesional skin. For single‐cell analysis, we analyzed the single‐cell data from suction blister material from AD lesions and HC skin at the antecubital fossa skin (4 ADs and 5 HCs) and full‐thickness skin biopsies (4 ADs and 2 HCs). The multiple proximity extension assays were performed in the serum samples from 36 AD patients and 28 HCs. Results: The single‐cell analysis identified unique clusters of fibroblasts, dendritic cells, and macrophages in the lesional AD skin. Spatial transcriptomics analysis showed the upregulation of COL6A5, COL4A1, TNC, and CCL19 in COL18A1‐expressing fibroblasts in the leukocyte‐infiltrated areas in AD skin. CCR7‐expressing dendritic cells (DCs) showed a similar distribution in the lesions. Additionally, M2 macrophages expressed CCL13 and CCL18 in this area. Ligand–receptor interaction analysis of the spatial transcriptome identified neighboring infiltration and interaction between activated COL18A1‐expressing fibroblasts, CCL13‐ and CCL18‐expressing M2 macrophages, CCR7‐ and LAMP3‐expressing DCs, and T cells. As observed in skin lesions, serum levels of TNC and CCL18 were significantly elevated in AD, and correlated with clinical disease severity. Conclusion: In this study, we show the unknown cellular crosstalk in leukocyte‐infiltrated area in lesional skin. Our findings provide a comprehensive in‐depth knowledge of the nature of AD skin lesions to guide the development of better treatments. [ABSTRACT FROM AUTHOR]

Allergic contact dermatitis (ACD) and atopic dermatitis (AD) are the most common human skin disorders. Although corticosteroids have been widely used to treat ACD and AD, the side effects of corticosteroids encourage researchers to explore new immunoregulatory treatments. Here, an immunomodulatory approach based on lipid nanoparticles carrying α-helical configurational melittin (α-melittin-NP) is developed to overcome T cell-mediated inflammatory reactions in an oxazolone (OXA)-induced contact hypersensitivity mouse model and OXA-induced AD-like mouse model. Intradermal injection of low-dose α-melittin-NPs prevents the skin damage caused by melittin administration alone and efficiently targeted lymph nodes. Importantly, melittin and α-melittin-NPs restrain RelB activity in dendritic cells (DCs) and further suppresses dendritic cell activation and maturation in lymph nodes. Furthermore, low-dose α-melittin-NPs leads to relief of antigen recognition-induced effector T cell arrest in the dermis and inhibited allergen-specific T cell proliferation and activation. Significantly, this approach successfully controls Th1-type cytokine release in the ACD model and restricts Th2-type cytokine and IgE release in the AD-like model. Overall, intradermal delivery of low-dose α-melittin-NPs efficiently elicits immunosuppression against T cell-mediated immune reactions, providing a promising therapeutic strategy for treating skin disorders not restricted to the lesion region. [ABSTRACT FROM AUTHOR]

Background: Recent studies in murine models of allergic contact dermatitis have shown that systemic treatment with pimecrolimus in contrast to tacrolimus did not inhibit the sensitization phase, whereas both compounds equivalently suppressed the inflammatory response in sensitized animals. This finding indicated a differential sensitivity of antigen-naïve and primed T cells towards pimecrolimus and tacrolimus. Methods: T cells obtained from healthy and allergic donors were subjected to primary and secondary stimulation by allogeneic or staphylococcal superantigen-presenting dendritic cells (DC). Human skin-derived, allergen-specific T cell clones from an atopic dermatitis patient were activated by anti-CD3 antibodies or by specific allergen-presenting DC. The inhibition of T cell proliferation and cytokine release by graded doses of calcineurin inhibitors was evaluated. Results: Primary stimulation of T cells was inhibited by pimecrolimus with an approximately 8-fold lower potency as compared with tacrolimus. In contrast, the secondary response of ex vivo expanded T cells activated by allogeneic or staphylococcal superantigen-presenting DC was inhibited by both compounds with equivalent potency. Likewise, both drugs showed very similar potency to inhibit the proliferation and cytokine synthesis from antigen- stimulated T cell clones and the induction of cytokines in Jurkat T cells. Conclusion: These data indicate that pimecrolimus has a selectivity for antigen-primed memory T cells not seen with tacrolimus. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Dendritic cells (DCs) represent a major portion within the infiltrate of atopic dermatitis (AD) lesions. As antigen-presenting cells they have the ability to regulate both the quantity and quality of T-cell responses and, thus, are likely to play a key role in the pathogenesis of T-cell-dominated skin diseases such as AD. Thus we sought to identify the DC repertoire occurring in AD patients. Methods: For this purpose, we phenotypically analyzed various defined DC subsets of AD patients and healthy controls in skin biopsies and peripheral blood by immunofluorescence staining. Results: In AD lesions, two inflammation-associated DC subsets with varying expression of costimulatory molecules occurred besides epidermal Langerhans cells (LCs) and dermal myeloid DCs (dmDCs) indigenously residing in normal skin: (1) CD1a+/CD1c+/FcεRI+/IgE+/CD207– myeloid DCs (mDCs) in the epidermis and dermis and (2) CD123+/BDCA-2+/CD45RA+/CD68+ plasmacytoid DCs (pDCs) in the dermis. In the peripheral blood of the patients, these cells exhibited an immature phenotype. Interestingly, we found FcεRI and cell-bound IgE to be expressed not only on myeloid, but also on plasmacytoid DCs from both the skin and peripheral blood of AD patients. Conclusions: It is tempting to speculate that the disease-regulating role of inflammatory DCs in AD is influenced by both FcεRI occupancy and their degree of maturity. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]