The role of M1/M2 macrophage polarization in primary Sjogren's syndrome

Background The purpose of this study was to investigate the role of macrophage polarization in the pathogenesis of primary Sjogren's syndrome (pSS).Methods Peripheral venous blood samples were collected from 30 patients with pSS and 30 healthy controls. Minor salivary gland samples were abtainted from 10 of these patients and 10 non-pSS controls whose minor salivary gland didn't fulfill the classification criteria for pSS. Enzyme-linked immuno sorbent assay was used to examine the serum concentration of M1/M2 macrophage related cytokines (TNF-a, IL-6, IL-23, IL-4, IL-10 and TGF-beta). Flow cytometry was used to examine the numbers of CD86+ M1 macrophages and CD206+ M2 macrophages in peripheral blood mononuclear cells (PBMCs). Immunofluorescence was used to test the infiltration of macrophages in minor salivary glands.Results This study observed a significant increase in pSS patients both in the numbers of M1 macrophages in peripheral blood and serum levels of M1-related pro-inflammatory cytokines (IL-6, IL-23 and TNF-alpha). Conversely, M2 macrophages were downregulated in the peripheral blood of pSS patients. Similarly, in the minor salivary glands of pSS patients, the expression of M1 macrophages was increased, and that of M2 macrophages was decreased. Furthermore, a significantly positive correlation was found between the proportions of M1 macrophages in PBMCs and serum levels of IgG and RF.Conclusions This study reveals the presence of an significant imbalance in M1/M2 macrophages in pSS patients. The M1 polarization of macrophages may play an central role in the pathogenesis of pSS.