Increased IL-17A expression in granulomas and in circulating memory T cells in sarcoidosis

Rheumatology (Oxford). 2012 Jan;51(1):37-46. doi: 10.1093/rheumatology/ker316. Epub 2011 Nov 10.

Abstract

Objective: Sarcoidosis is a systemic inflammatory disorder characterized by granulomas. Although the aetiology is unknown, sarcoidosis is thought to be mediated by Th1 lymphocytes. Recently, IL-17A has been implicated in granuloma formation in various diseases, including tuberculosis. Therefore, we hypothesized that Th17 cells play a role in sarcoidosis, paralleling recent findings in autoimmune diseases such as RA. The aim of our study was to investigate the role of Th17 cells in sarcoidosis.

Methods: T cells were investigated by intracellular flow cytometry and immunohistochemistry, in blood, bronchoalveolar lavages (BALs) and bronchial mucosal biopsies from a cohort of newly diagnosed sarcoidosis patients and healthy controls.

Results: Circulating memory CD4(+) T-cell populations of sarcoidosis patients contained significantly increased proportions of IL-17A(+) cells when compared with healthy controls. Interestingly, proportions of IL-17A/IFN-γ and IL-17A/IL-4 double-producing cells were significantly increased in blood of sarcoidosis patients and were present in substantial numbers in BAL. In granuloma-containing, but not in non-granulomatous sarcoidosis biopsies, we found significantly increased numbers of IL-17A(+) T cells, located in and around granulomas throughout the lamina propria. IL-22(+) T cells were increased in the subepithelial layer.

Conclusions: Enhanced IL-17A expression in granulomas and the presence of IL-17A(+), IL-17A(+)IFN-γ(+) and IL-17A(+)IL-4(+)memory Th cells in the circulation and BAL indicate Th17 cell involvement in granuloma induction or maintenance in sarcoidosis. Therefore, neutralization of IL-17A activity may be a novel strategy to treat sarcoidosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biopsy
  • Bronchoalveolar Lavage Fluid / immunology
  • Case-Control Studies
  • Female
  • Granuloma / immunology*
  • Granuloma / pathology
  • Humans
  • Immunologic Memory
  • Interferon-gamma / metabolism
  • Interleukin-17 / metabolism*
  • Interleukin-17 / physiology
  • Interleukins / metabolism
  • Lung / pathology
  • Male
  • Sarcoidosis, Pulmonary / immunology*
  • Sarcoidosis, Pulmonary / pathology
  • T-Lymphocyte Subsets / immunology
  • Th17 Cells / immunology*
  • Tumor Necrosis Factor-alpha / metabolism
  • Young Adult

Substances

  • Interleukin-17
  • Interleukins
  • Tumor Necrosis Factor-alpha
  • Interferon-gamma
  • interleukin-22