Plasmacytoid dendritic cells (pDCs) represent a specialized dendritic cell population that exhibit plasma cell morphology, express CD4, CD123, blood-derived dendritic cell antigen-2 (BDCA-2) and Toll-like receptor (TLR)7 and TLR9 within endosomal compartments. When activated, pDCs are capable of producing large quantities of type I IFNs (mainly IFN-a/b), which provide antiviral resistance and link the innate and adaptive immunity. While generally lacking from normal skin, pDCs infiltrate the skin and appear to be involved in the pathogenesis of several inflammatory, infectious (especially viral) and neoplastic entities. In recent years, pDC role in inflammatory/ autoimmune skin conditions has been extensively studied. Unlike type I IFN-mediated protective immunity that pDCs provide at the level of the skin by regulated sensing of microbial or selfnucleic acids upon skin damage, excessive sensing may elicit IFN-driven inflammatory/autoimmune diseases. In this review, focus will be on the role of pDCs in cutaneous inflammatory/ autoimmune dermatoses.

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Plasmacytoid dendritic cells (PDCs) are specialized dendritic cells with a significant role in antiviral resistance. 1,2 Plasmacytoid dendritic cells have never been studied in orf infection.

pDCs constitute a central component of the inflammatory host response in inflamed warts, possibly contributing to their regression through production of type I interferons.

BackgroundHailey-Hailey disease (HHD) is an inherited blistering dermatosis characterized by recurrent erosions and erythematous plaques that generally manifest in intertriginous areas. Genetically, HHD is an autosomal dominant disease, resulting from heterozygous mutations in ATP2C1, which encodes a Ca2+/Mn2+ATPase. In this study, we aimed at identifying and analyzing mutations in five patients from unrelated families diagnosed with HHD and study the underlying molecular pathogenesis.ObjectivesTo genetically study Lebanese families with HHD, and the underlying molecular pathogenesis of the disease.MethodsWe performed DNA sequencing for the coding sequence and exon-intron boundaries of ATP2C1. Heat shock experiments were done on several cell types. This was followed by real-time and western blotting for ATP2C1, caspase 3, and PARP proteins to examine any possible role of apoptosis in HHD. This was followed by TUNEL staining to confirm the western blotting results. We then performed heat shock experiments on neonatal rat primary cardiomyocytes.ResultsFour mutations were detected, three of which were novel and one recurrent mutation in two families. In order for HHD to manifest, it requires both the genetic alteration and the environmental stress, therefore we performed heat shock experiments on fibroblasts (HH and normal) and HaCaT cells, mimicking the environmental factor seen in HHD. It was found that stress stimuli, represented here as temperature stress, leads to an increase in the mRNA and protein levels of ATP2C1 in heat-shocked cells as compared to non-heat shocked ones. However, the increase in ATP2C1 and heat shock protein hsp90 is significantly lower in HH fibroblasts in comparison to normal fibroblasts and HaCaT cells. We did not find a role for apoptosis in the pathogenesis of HHD. A similar approach (heat shock experiments) done on rat cardiomyocytes, led to a significant variation in ATP2C1 transcript and protein levels.ConclusionThis is the first genetic report of HHD from Lebanon in which we identified three novel mutations in ATP2C1 and shed light on the molecular mechanisms and pathogenesis of HHD by linking stress signals like heat shock to the observed phenotypes. This link was also found in cultured cardiomyocytes suggesting thus a yet uncharacterized cardiac phenotype in HHD patients masked by its in-expressivity in normal health conditions.