Cells with regulatory function of the innate and adaptive immune system in primary Sjögren’s syndrome

Summary The aim of the present study was to describe subsets of cells with regulatory properties in primary Sjögren’s syndrome (pSS), and to correlate these cell populations with clinical symptoms. Among the 32 investigated patients, 23 had extraglandular manifestations (EGMs), while nine had only glandular symptoms. Twenty healthy individuals served as controls. The percentages of natural killer (NK), natural killer T cells (NK T), interleukin (IL)-10 producing T regulatory type 1 (Tr1) cells and CD4+CD25+ regulatory T cells (Treg) cells were determined by flow cytometry and serum cytokine levels of IL-4, IL-6, IL-10, tumour necrosis factor (TNF)-α and interferon (IFN)-γ were evaluated by enzyme-linked immunosorbent assay (ELISA). Functional tests were carried out to assess the suppressor properties of Treg cells in patients and controls. Peripheral NK, NK T and Tr1 cell percentages were elevated in pSS, while CD4+CD25+ Treg cells showed reduced frequencies in patients compared to controls. In pSS, elevated percentages of NK T, Tr1 and CD4+CD25+ Treg cells were observed in patients with EGMs, when compared to patients with sicca symptoms only. CD4+CD25+ Treg cell percentages showed a negative correlation with sialometry values. The in vitro functional assay demonstrated lower suppression activity of CD4+CD25+ Treg cells in patients compared to controls. Serum IL-6 and TNF-α levels were elevated, while IL-10 was decreased in patients compared to controls. Negative correlation was found between IL-10 levels and the percentages of Tr1 cells. Changes in the investigated subsets of regulatory cells in pSS may contribute to the development and progression of the disease.