Decreased BAFF-R on peripheral lymphocytes associated with increased disease activity in primary Sjogren's syndrome and systemic lupus erythematosus. [Ann Rheum Dis] Journal article

OBJECTIVE: To analyse B-cell activating factor (BAFF) receptor (BAFF-R) on peripheral lymphocytes from patients with primary Sjögren's syndrome (pSS) and systemic lupus erythematosus (SLE).
PATIENTS AND METHODS: Peripheral blood mononuclear cells from 20 pSS, 19 SLE patients and 15 controls were examined by flow cytometry to investigate BAFF-R mean fluorescence intensity (MFI) on lymphocytes. BAFF-R mRNA level from isolated blood B cells of 9 pSS patients and 8 controls was assessed by real-time quantitative RT- PCR. BAFF serum level was determined by ELISA.
RESULTS: In all subjects, BAFF-R was expressed on all naïve CD27- and memory CD27+ B cells and was present on <0.5% of T cells. BAFF-R expression on B cells was significantly decreased in pSS patients as compared with controls (MFI=7.8 vs 10.6, p=0.001) and was intermediate in SLE patients (MFI=9.5). Serum BAFF level was inversely correlated with BAFF-R MFI (p=0.007) but not because of competition between endogenous BAFF (at observed concentrations in patients) and the monoclonal antibody (11C1) detecting BAFF-R. BAFF-R mRNA level did not differ between pSS patients and controls (p=0.48). BAFF-R MFI decreased after overnight culture with rhBAFF (from 32.5 to 25.4, p=0.03). Contrary to serum BAFF level, BAFF-R expression was correlated with extraglandular involvement in pSS and SLE Disease Activity Index.
CONCLUSIONS: /B>BAFF-R expression is reduced on peripheral B cells of pSS and SLE patients. This downregulation occurs through a post-transcriptional mechanism and could be the consequence of chronic BAFF increase. BAFF-R level on B eclls could be a novel activity bio-marker in autoimmune diseases.

Ann Rheum Dis