B-lymphocyte activating factor levels are increased in patients with Wegener's granulomatosis and inversely correlated with ANCA titer.

Circulating autoantibodies against neutrophils (ANCA) are a distinctive finding in patients with Wegener's granulomatosis (WG). B-lymphocyte activating factor (BAFF) promotes autoantibody production by increasing B cell survival and proliferation. We investigated serum BAFF levels (s-BAFF) in a WG patient cohort in relation to ANCA titers and disease activity. Baseline data were obtained in twenty-two WG patients (55% female, age 44 years, disease duration 1 year). S-BAFF was determined by capture ELISA and associations between s-BAFF, clinical (Birmingham Vasculitis Activity Score (BVAS), Vasculitis Damage Index (VDI) and Disease Extent Index (DEI)) and biochemical (C-reactive protein (CRP), IgG and ANCA) disease measures were analysed in a cross sectional as well as longitudinal analysis. S-BAFF was increased in WG patients compared to healthy controls (1.8 vs. 0.55 ng/ml, p < 0.01). S-BAFF was higher in ANCA negative than ANCA-positive WG sera (2.16 vs. 1.29 ng/ml, p < 0.01), correlated independently and inversely with ANCA levels (Rs -0.48, p < 0.01) but did not correlate with CRP, BVAS, DEI or VDI scores. Individual s-BAFF profiles were stable over time in 68% of patients. The finding of a negative correlation between ANCA levels and s-BAFF that is independent of steroid treatment indicates that BAFF does not directly drive ANCA production in WG.