Background: Increased levels of B lymphocyte stimulator (BLyS) have been detected in serum from patients with systemic lupus erythematosus and rheumatoid arthritis. Objective: To determine the level of BLyS in serum from patients with primary's Sjögren's syndrome (SS), another autoimmune disease in which B cell activation is high. Methods: Serum samples from 49 patients with primary SS according to the revised European criteria were assayed for BLyS, quantitative immunoglobulins, and autoantibody levels and compared with samples from 47 healthy control subjects. Results: The median level of BLyS was 5.99 ng/ml (25th-75th centile range 3.20-8.93 ng/ml) in SS v 2.49 ng/ml (25th-75th centile range 1.96-2.96 ng/ml) in healthy controls (p<0.001). More importantly, among patients with SS, the presence of anti-SSA antibodies was associated with significantly higher levels of BLyS (medians 7.90 ng/ml v 3.70 ng/ml; p=0.008) as was the presence of anti-SSB antibodies (medians 7.14 ng/ml v 3.70 ng/ml; p=0.02) and of rheumatoid factor (medians 7.70 ng/ml v 3.80 ng/ml; p=0.016). The level of BLyS in three patients with a monoclonal gammopathy was higher than in the other patients (medians 26.53 ng/ml v 5.92 ng/ml; p=0.13). Higher levels of BLyS were associated with higher levels of gammaglobulins and IgG. There was a strong correlation between BLyS and rheumatoid factor level (r=0.71, p<0.0001), anti-SSA IgG level (r=0.32, p=0.02) and anti-SSA IgM level (r=0.39, p=0.006). Conclusion: In human SS the level of BLyS correlates with the level of autoantibodies. Thus, BLyS may play a part in activating specific autoreactive B cells and modulating the level of production of autoantibodies which are the hallmark of the disease. These findings raise the possibility of a novel therapeutic approach in human SS.

Objective: To estimate the effect of Belimumab on the heterogeneity of peripheral blood lymphocytes and monocytes subsets in systemic lupus erythematosus (SLE).Methods: There were three groups of populations, namely health controls (HC, n = 92), SLE patients treated (n = 26) and un-treated with BAFF (n = 155) in the present study. Cell subsets of CD3+T cells, CD3+CD4+T cells, CD3+CD8+T cells, CD19+B cells, CD16+CD56+NK cells, CD14+HLA-DR+monocytes, CD14+CD206+monocytes and CD14+CD163+monocytes were estimated by flow cytometry. Results: Compared with HC group, SLE patients had a higher level of CD3+T cells and CD3+CD8+T cells, but a lower level of CD3+CD4+T cells, CD16+CD56+NK cells, CD14+CD206+monocytes, and CD14+CD163+monocytes. Besides, the ratio of CD3+CD4+/CD3+CD8+T cells was much lower in SLE patients. Belimumab could effectively decrease CD19+B cells but increase CD3+T cell and CD3+CD8+T cells in the peripheral blood of SLE patients. Moreover, SLE patients had decreased CD14+CD206+ monocytes and CD14+CD163+ monocytes in peripheral blood, while Belimumab therapy did not affect the heterogeneity of monocytes in SLE.Conclusions: Our results revealed the heterogeneity of lymphocytes and monocytes in SLE patients. The clinical efficacy of Belimumab in SLE treatment is remarkable due to its significant effect on down-regulating B cell but up-regulating CD3+T cell and CD3+CD8+T cells in SLE.