B-cell activating factor of the tumour necrosis factor family expression in blood monocytes and T cells from patients with primary Sjogren's syndrome

We investigated B-cell activating factor of the tumour necrosis factor family (BAFF) level in peripheral blood mononuclear cells (PBMCs), monocytes and T cells from patients with primary Sjogren's syndrome (pSS) and controls both ex vivo and in vitro after cytokine stimulation. PBMCs, monocytes and T cells were isolated from 15 patients with pSS and 17 controls. Cells were cultured alone or with interferon (IFN)alpha, IFN gamma and interleukin 10 (IL-10). T cells were stimulated with phytohaemagglutin and anti-CD3. BAFF protein was assessed by enzyme-linked immunosorbent assay. Ex vivo, no difference was observed in BAFF mRNA level in PBMCs and monocytes from patients and controls. Blood monocytes were the main cell type secreting BAFF both in patients and controls. In vitro, after IFN alpha stimulation, BAFF mRNA level was significantly higher in cells from patients than from controls (63.8 versus 20.7, P = 0.03). T cells from patients secreted a higher level of BAFF protein than those from healthy donor cells (17.4 versus 2.9 pg/ml, respectively, P = 0.04) but at a lower level than that from monocytes. Stimulation of T cells did not change BAFF secretion level. The induction of Th17 cells showed no increased BAFF expression. In conclusion, similar to epithelial cells, blood monocytes in patients with pSS show increased production of BAFF under IFN alpha, which confirms the involvement of IFN alpha in pSS. BAFF expression is also increased in blood T cells of such patients, independently of T-cell stimulation.