Background Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease affecting predominantly exocrine glands such as salivary and lacrimal glands. Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a new clinical concept of multi-organ diseases, which is characterized pathologically by the infiltration of IgG4-bearing plasma cells into involved organs. However, some pSS patients showed infiltration of IgG4+ plasma cells in exocrine glands.

Objectives We aim to investigate the characteristics of primary Sjögren's syndrome (pSS) patients with IgG4+ plasma cells in labial salivary glands (LSGs).

Methods 336 patients with pSS were enrolled. The LSG tissues from pSS patients were stained with monoclonal antibodies to IgG4 and IgG. Patients were divided into three subgroups according to histopathologic infiltration degree of IgG4⁺ plasma cells. The clinical and serological characteristics of patients were compared.

Results 336 patients were divided into three groups according to infiltration degree of IgG4⁺ plasma cells: slight-IgG4 group (n=194), moderate-IgG4 group (n=106) and high-IgG4 group (n=36). The results showed that the higher IgG4⁺ plasma cells expression, the lower positive rates of serum anti-SSA, anti-SSB, anti-nuclear antibodies (ANA) and rheumatoid factor (RF). The comparison of extraglandular manifestations of three groups indicated that patients in high-IgG4 expression group showed a highest frequency of interstitial lung disease (30.6%) and tubulointerstitial nephritis (13.9%), whereas a lowest frequency of leucopaenia (13.9%), thrombocytopaenia (11.1%) and abnormal thyroidal function (0%).

Conclusions The results showed that a considerable proportion of pSS patients could manifest abundant IgG4+ plasma cells infiltration in LSGs. These patients have unique laboratory and clinical characteristics. These findings may help further understand pSS, IgG4-RD, and the role of IgG4⁺ plasma cells in autoimmune diseases.

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Disclosure of Interest None declared