Roles of IL-17, Th1, and Tc1 cells in patients with IgG4-related sclerosing sialadenitis.

OBJECTIVES/HYPOTHESIS Immunoglobulin G4 (IgG4)-related sclerosing sialadenitis is a recently recognized disease entity characterized by high serum IgG4 concentration and IgG4-producing plasma cell expansion in affected organs, which show fibrotic or sclerotic changes. However, little is known about the roles of CD4+ and CD8+ T cells or interleukin (IL)-17 in this disease. The purpose of this study was to evaluate the characteristics of CD4+ and CD8+ T cells and IL-17 in patients with IgG4-related sclerosing sialadenitis. STUDY DESIGN A retrospective clinical study at the Yamagata University School of Medicine. METHODS The patient group consisted of six males and four females with an average age of 57.9 years (range, 38 to 73 years). Subsets of T helper (Th)1, Th2, T cytotoxic type (Tc)1, and Tc2 cells from patients with IgG4-related sclerosing sialadenitis were examined by using intracellular cytokine flow cytometry. Expression of IL-17 in the patients' lesions was also investigated immunohistochemically. RESULTS Six patients with IgG4-related sclerosing sialadenitis with high ratios of IgG4/IgG and prominent infiltration of IgG4-positive plasmacytes in the involved salivary glands had systemic complications, including pancreatitis, retroperitoneal fibrosis, and/or inflammatory pseudotumor of the lung after the initial swelling of the salivary glands. Populations of Th1 and Tc1 cells were significantly greater in IgG4-related sclerosing sialadenitis than in the controls (P < .05), but Th2 and Tc2 cell populations were not significantly increased. Expression of IL-17 was observed in the lesions of affected patients. CONCLUSIONS Increases in Th1 and Tc1 cell populations and IL-17 expression might be involved in the mechanism of pathogenesis of IgG4-related sclerosing sialadenitis.