- IL-36 cytokines are composed of three agonists, namely IL-36α, IL-36β, and IL-36γ, and a natural antagonist, IL-36Ra (Sims and Smith, 2010). IL-36 cytokines are abundantly expressed by the skin and other epithelial tissues, whereas the IL-36 receptor (IL-36R) is expressed by skin and immune cells, including dendritic cells (DCs) (Gabay and Towne, 2015; Vigne et al., 2011). Earlier studies have demonstrated that IL-36 cytokines play important roles in the development of psoriasiform inflammation by enhancing the function of T helper type 17 cytokines (Carrier et al., 2011; Tortola et al., 2012).
- The IL-1 signaling pathway has been shown to play a critical role in the pathogenesis of chronic, autoinflammatory skin diseases such as psoriasis. However, the exact cellular and molecular mechanisms have not been fully understood. Here, we show that IL-1β is significantly elevated in psoriatic lesional skin and imiquimod-treated mouse skin. In addition, IL-1R signaling appears to correlate with psoriasis disease progression and treatment response. IL-1 signaling in both dermal γδ T cells and other cells such as keratinocytes is essential to an IMQ-induced skin inflammation.
- Conventional dendritic cells (cDCs) are composed of heterogeneous subsets commonly arising from dendritic cell (DC)−committed progenitors. A population of CD301b-expressing DCs has recently been identified in non-lymphoid barrier tissues such as skin. However, whether CD301b+ DCs in the skin represent an ontogenetically unique subpopulation of migratory cDCs has not been fully addressed. Here, we demonstrated that CD301b+ dermal DCs were distinct subpopulation of FMS-like tyrosine kinase 3 ligand (FLT3L)−dependent CD11b+ cDC2 lineage, which required an additional GM-CSF cue for the adequate development.
- IL-9 is present in psoriatic lesions and is produced by lymphocytes. However, it is not known whether this cytokine is induced by relevant pathogenic triggers of psoriasis, such as Streptococcus pyogenes. Here we addressed the production of IL-9 in response to various pathogens in a psoriatic ex vivo model. Extracts of S. pyogenes and Candida albicans triggered the production of IL-9 and also IL-17A and IFN-γ. This induction was dependent on the interaction between CLA+ T cells and epidermal cells.
- 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 is a chronic inflammatory disease with a complex genetic architecture. To date, the psoriasis heritability is only partially explained. However, there is increasing evidence that the missing heritability in psoriasis could be explained by multiple genetic variants of low effect size from common genetic pathways. The objective of this study was to identify new genetic variation associated with psoriasis risk at the pathway level. We genotyped 598,258 single nucleotide polymorphisms in a discovery cohort of 2,281 case-control individuals from Spain.
- Genetic variations in the proinflammatory cytokine IL-23 are associated with psoriasis, a common, inflammatory skin disorder (Nair et al., 2009). IL-23 is primarily produced by dendritic cells (DCs) and plays a pathogenic role in psoriasis by directing the development of T helper type 17 cells (Di Cesare et al., 2009). Langerhans cells (LCs), the main DC subtype in the epidermis, can participate in both immunity and the induction of tolerance (Igyarto et al., 2011; Seneschal et al., 2012), yet their role in psoriasis remains unclear.