- The phosphoinositide 3-kinase (PI3K) pathway plays a key role in many cellular processes, including cell proliferation, survival, and protein synthesis, with the PI3K isoform, PI3Kδ, involved in normal T-cell development and function (Jarmin et al., 2008; Lucas et al., 2016; Vanhaesebroeck et al., 2012). Evidence to suggest that PI3K signaling might play a role in psoriasis comes from reports of increased expression of phosphorylated protein kinase B, mammalian target of rapamycin, and ribosomal protein S6 (pS6), which are downstream in the PI3K signaling pathway, in lesional psoriatic skin compared with nonlesional skin and healthy controls (Buerger et al., 2013; Madonna et al., 2012; Rosenberger et al., 2007).
- Generalized pustular psoriasis (GPP) is the most severe psoriasis variant. Mutations in the IL-36 antagonist IL36RN, in CARD14 or AP1S3 provide genetic evidence for autoinflammatory etiology but cannot explain its pathogenesis completely. Here we demonstrate that unopposed IL-36 signaling promotes antigen-driven and likely pathogenic T-helper type 17 (Th17) responses in GPP. We observed that CD4+ T cells in blood and skin lesions of GPP patients were characterized by intense hyperproliferation, production of the GPP key mediator, IL-17A, and highly restricted TCR repertoires with identical T-cell clones in blood and skin lesions, indicating antigen-driven T-cell expansions.
- Innate immune processes are central in the development of the chronic inflammatory skin disease psoriasis. Studying stimulation of keratinocytes, monocytes, and dendritic cells by type I interferons or ligation of Toll-like receptors 1/2, 2/6, or 7, but not 7/8, resulted in enhanced surface expression and secretion of CXC chemokine ligand (CXCL) 16. The corresponding CXC chemokine receptor 6 was expressed on neutrophils whose recruitment into skin is important, especially in early psoriatic disease.
- Psoriasis vulgaris is an inflammatory skin disease caused by hyperactivated T cells regulated by positive and negative mechanisms; although the former have been much studied, the latter have not. We studied the regulatory mechanism mediated by myeloid-derived suppressor cells (MDSCs) and showed that MDSCs expanded in melanoma patients express dendritic cell-associated heparan sulfate proteoglycan-dependent integrin ligand, a critical mediator of T-cell suppressor function. We examined expansion of DC-HIL+ MDSCs in psoriasis and characterized their functional properties.
- Transcriptome studies of psoriasis have identified robust changes in mRNA expression through large-scale analysis of patient cohorts. These studies, however, have analyzed all mRNA changes in aggregate, without distinguishing between disease-specific and nonspecific differentially expressed genes (DEGs). In this study, RNA-seq meta-analysis was used to identify (1) psoriasis-specific DEGs altered in few diseases besides psoriasis and (2) nonspecific DEGs similarly altered in many other skin conditions.
- We read with great interest the article by D’Erme et al. (2015) entitled “IL-36γ (IL-1F9) Is a Biomarker for Psoriasis Skin Lesions.” By performing an unsupervised gene cluster analysis, the authors identified genes specifically expressed within different subsets of inflammatory skin diseases; among these, psoriasis-associated genes were further analyzed to show that IL-36γ showed the strongest association with psoriasis when compared with the other skin diseases. The authors confirmed this specificity, showing high levels of IL-36γ both in skin by immunohistochemistry and in serum by ELISA assay.
- The clinical extent of psoriasis pathology is regulated in part by defects in immune networks, including a defect in the suppressive actions of regulatory T cells. Recently, CD14+ HLA-DR–/low monocytic myeloid-derived suppressor cells (Mo-MDSCs) have been shown to suppress T-cell activation as one of their suppressive mechanisms. However, little is known about the role of Mo-MDSCs and their functional relationship to T-cell suppression in relation to human chronic immune-mediated inflammatory diseases, including psoriasis.