Increased Frequency of Cells Secreting Interleukin‐6 and Interleukin‐10 in Peripheral Blood of Patients with Primary Sjögren's Syndrome

Abstract

Sjögren's syndrome (SS) is a chronic autoimmune disease of exocrine glands. There is increasing evidence that interferon-γ (IFN-γ) plays a role in the pathogenesis of SS. It has also been suggested that other type 1 cytokines, as well as interleukin-6 (IL-6), IL-10 and transforming growth factor-β, are important in the induction and/or maintenance of SS. The aim of this study was to investigate the type 1/type 2 cytokine pattern in peripheral blood of primary SS patients. The enzyme-linked immunospot (ELISPOT) assay was performed to quantify the number of mononuclear cells (MNC) secreting IFN-γ, IL-6 and IL-10 in peripheral blood samples from 33 patients with primary SS and 12 healthy controls. The mean number of cells secreting IFN-γ was 9/10⁵ MNC in the SS patient group, and 4/10⁵ MNC in the control group (P = 0.73). Fifteen of the SS patients had anti-Ro 52 kDa antibodies in serum. In this patient group the mean number of cells secreting IFN-γ was 4/10⁵ MNC, while in the patient group without such antibodies the mean number of cells secreting IFN-γ was 14/10⁵ MNC (P = 0.04). The mean number of cells secreting IL-6 was 12 000/10⁵ MNC in the SS patient group, and 5000/10⁵ MNC in the control group (P = 0.01). The mean number of cells secreting IL-10 was 270/10⁵ MNC in the SS patient group, and 180/10⁵ MNC in the control group (P = 0.04). The SS patients had a significantly higher number of cells secreting IL-6 and IL-10 in peripheral blood than the healthy controls, which may facilitate B-cell activation and production of autoantibodies.