Interleukin-36 promotes systemic Type-I IFN responses in severe psoriasis.

Abstract

Psoriasis is an immune-mediated skin disorder associated with severe systemic co-morbidities. Both chronic and acute forms of the disease are characterised by abnormal interleukin (IL)-36 signalling. While the mechanisms whereby IL-36 promotes cutaneous inflammation are well established, its systemic effects have not been investigated. To address this issue, we initially measured leukocyte gene expression in generalised pustular psoriasis, an acute disease variant caused by mutations of the IL-36 receptor antagonist. By undertaking whole-blood and neutrophil RNA-sequencing in affected individuals, we identified a Type-I IFN signature, which correlated with IL-36 signalling up-regulation. We then validated these observations in patients with chronic plaque psoriasis. Finally, we demonstrated that IL-36 acts directly on plasmacytoid dendritic cells, where it potentiates Toll-like Receptor (TLR)-9 activation and IFN production. This effect was mediated by the induction of PLSCR1, an endosomal TLR-9 transporter. These results define an IL-36/TLR-9/Type-I IFN axis that could be targeted for the treatment of psoriasis co-morbidities.