IL-17-producing [gamma][delta] T cells and innate lymphoid cells

• Published in: European journal of immunology Vol. 42; no. 9; pp. 2221 - 2231
• Main Authors: Sutton, Caroline E, Mielke, Lisa A, Mills, Kingston H G
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.09.2012
• Subjects: Autoimmune diseases; Cytokines; Immune system; Lymphocytes; T cell receptors
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/eji.201242569

The inflammatory cytokine IL-17 plays a critical role in immunity to infection and is involved in the inflammatory pathology associated with certain autoimmune diseases, such as psoriasis and rheumatoid arthritis. While CD4+ and CD8+ T cells are important sources of this cytokine, recent evidence has suggested that [gamma][delta] T cells and a number of families of innate lymphoid cells (ILCs) can secrete IL-17 and related cytokines. The production of IL-17 by [gamma][delta] T cells appears to be largely independent of T-cell receptor act-ivation and is promoted through cytokine signalling, in particular by IL-23 in combination with IL-1[beta] or IL-18. Therefore IL-17-secreting [gamma][delta] T cells can be categorised as a family of cells similar to innate-like lymphoid cells. IL-17-secreting [gamma][delta] T cells function as a part of mucosal defence against infection, with most studies to date focusing on their response to bacterial pathogens. [gamma][delta] T cells also play a pathological role in certain autoimmune diseases, where they provide an early source of IL-17 and IL-21, which initiate responses mediated by conventional IL-17-secreting CD4+ T cells (Th17 cells). ILCs lack an antigen receptor or other linage markers, and ILC subsets that express the transcriptional factor ROR[gamma]t have been found to secrete IL-17. Evidence is emerging that these newly recognised sources of IL-17 play both pathological and protective roles in inflammatory diseases as discussed in this article. [PUBLICATION ABSTRACT]