Correlation of Memory B Cell and B Cell Activation Factor with Clinical Indicators in Primary Sj?gren's Syndrome Patients and Their First-degree Relatives

  Objectives  To investigate the expression of CD19+CD27+ (memory B cell) and B cell activation factor(BAFF), in the peripheral blood of patients with primary Sjögren's syndrome (pSS) and their relatives and to analyze the correlations of the cells with clinical indicator.

  Methods  Peripheral venous bloodsamples were collected from 41 newly diagnosed pSS patients[females, age 48.7±9.1 years, anti-SSA/SSB (+) 73.2%] from Sjögren's International Collaborative Clinical Alliance(SICCA) and Peking Union Medical College Hospital(PUMCH), and 27 healthy controls (females, age 47.0±3.8 years) and 7 first-degree relatives of the patients (females, age 50.1±5.0 years). The levels of memory B cells in the peripheral blood were measured by flow-cytometric. The level of BAFF in serum was determined with enzyme-linked immunosorbent assay (ELISA). Clinical indicators including IgG, IgA, IgM, C3, C4, Focus score, 5-min salivary rate, ocular score, Schirmer test results were tested simultaneously.

  Results  The level of memory B cell in the blood of pSS patients was 11.10%±5.10%, which was significantly higher than that of the healthy controls 9.24%±6.99% (P=0.0002), but was not significant differences between pSS patients and their first-degree relatives (P>0.05). BAFF in pSS was 1.18±0.72 ng/ml, which was significantly higher than that of the healthy controls (0.43±0.19 ng/ml) (P=0.0005) and than that of their first-degree relatives (0.56±0.11 ng/ml) (P=0.015). CD27+ B cell were positively correlated with 5-min salivary rate (r=0.345, P=0.027), negatively correlated with ocular score (r=-0.321, P=0.041); however, it was not correlated with IgG, IgA, IgM, C3, C4, focus score, and Schirmer test results. BAFF was not correlated with IgG, IgA, IgM, C3, C4, focus score, 5-min salivary rate, ocular score, and Schirmer test (P > 0.05).

  Conclusions  The memory B cell is highly expressed in pSS patients and their first-degree relatives and is negatively correlated with clinical indicators, suggesting that memory B cell may migrate from peripheral tissues to the gland tissues during the pathogenesis of pSS. BAFF level is remarkably higher in pSS patients than in their first-degree relatives and in healthy controls, suggesting that BAFF may be involved in the development of pSS but is not parallel with the severity of this disease.