Characteristics of primary Sjögren's syndrome patients with IgG4 positive plasma cells infiltration in the labial salivary glands.

The purpose of this study was to investigate the characteristics of primary Sjögren's syndrome (pSS) patients with IgG4 positive (IgG4+) plasma cell infiltration in labial salivary glands (LSGs). Paraffin sections of LSGs from 336 pSS patients were stained with IgG4 and IgG monoclonal antibodies. According to the infiltration of IgG4+ plasma cells, patients were divided and clinical and serological characteristics were analyzed and compared. Based on the infiltration of IgG4+ plasma cells in the LSGs, patients were divided into three subgroups, low IgG4, moderate IgG4, and high IgG4 groups. A negative association between the number of infiltrated IgG4+ plasma cells and the disease characteristics was observed. We found that the higher the IgG4+ expression in plasma cells, the lower the positive rates of serum anti-SSA antibodies, anti-SSB antibodies, antinuclear antibodies (ANA), and rheumatoid factor (RF). Besides, patients from the high IgG4 group had the highest frequency of interstitial lung disease (ILD, 30.6%) and tubulointerstitial nephritis (TIN, 13.9%), but the lowest frequency of leucopenia (13.9%), thrombocytopenia (11.1%), and abnormal thyroidal function (0%). PSS patients with different IgG4+ plasma cells infiltration in the LSGs had distinctive clinical and laboratory characteristics. It may help us to further understand the role of IgG4+ plasma cells in pSS.