The role of IL-33 in regulating skin immunity and skin carcinogenesis
File(s)
Author(s)
Ward, Sophie
Type
Thesis
Abstract
Lymphoid stress-surveillance (LSS) refers to the capacity of tissue resident intraepithelial lymphocytes (IEL) to directly sense epithelial cell (EC) dysregulation and initiate a reparative response. Dendritic epidermal T cells (DETC) in the skin are potent producers of IL-13 upon epithelial dysregulation, which regulates EC function, promotes tissue homeostasis and protects against skin carcinogenesis. This may be due to its prominent effect on basal EC, where IEL-derived IL-13 enables a canonical EC stress-response with the expression of Il33 RNA. IL-33 is an abundant cytokine ‘alarmin’ which is constitutively expressed in the nucleus of basal skin EC but is rapidly released upon epithelial challenge. Here I show that LSS in the skin regulates the expression of IL-33 protein in EC during health as well as its release following epithelial damage. LSS does not regulate the fellow family member epithelial alarmin, IL-1, in EC. The IL-33 receptor, ST2, is predominantly expressed on skin resident and infiltrating regulatory T cells (TReg), with skin ST2+TReg localizing in close association with IL-33+ basal EC. I demonstrate that ST2-signalling in skin TReg promotes a more immunosuppressive and reparative phenotype in these cells. Absence of the IL-33/ST2 axis alters EC differentiation and phenotype, with EC aberrantly expressing stress-antigens, distinct keratins and pro-inflammatory cytokines, and the tissue displays reduced barrier integrity, as demonstrated by an increase in trans-epidermal water loss. Moreover, IL-33/ST2-signalling aids in restoring the skin barrier after epidermal abrasion by tape stripping, regulates immune infiltration during skin inflammation and protects against EC tumour outgrowth during cutaneous two-stage chemical carcinogenesis. Together my findings suggest, that IL-33, downstream of LSS, mediate direct EC-TReg cross-communication, and that this molecular axis further supports tissue homeostasis and protects against skin cancer development.
Version
Open Access
Date Issued
2019-10
Date Awarded
2020-03
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Strid, Karin Jessica
Botto, Marina
Publisher Department
Department of Immunology and Inflammation
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)