Concentrations of BAFF correlate with autoantibody levels, clinical disease activity, and response to treatment in early rheumatoid arthritis

Objective: To determine whether levels of B cell activating factor (BAFF), a member of the tumor necrosis factor family, relate to autoantibody levels, disease activity, and response to treatment in patients with early rheumatoid arthritis (ERA). Methods: BAFF was measured by ELISA in 48 early RA patients; 21 were examined serially. These data were compared with 49 controls with longstanding RA (LSRA), 48 disease controls (DC), and 50 healthy controls (HC). Results: BAFF levels were higher in ERA, compared with DC and HC [median 4.3 ng/ml (5th-95th: 0.8-38.8) vs 0.9 ng/ml (5th-95th: 0.7-4.5) and 2.0 ng/ml (5th-95th: 0.7-5.68), respectively; p <10(-4 )both comparisons], but not with LSRA controls [median 8.7 ng/ml (5th-95th: 0.8-46.1); p = nonsignificant]. BAFF correlated with the titers of IgM rheumatoid factor and anti-cyclic citrullinated peptide autoantibody (r = 0.76 and r = 0.49; p < 0.00001, p = 0.0001 for the 2 correlations), and with the number of swollen joints (r = 0.37; p = 0.01). The followup study of 21 methotrexate-treated ERA patients revealed reduced levels of BAFF, with parallel improvement in clinical activity and decrease in autoantibody titers. Conclusion: Elevated BAFF in a subset of ERA patients is related to autoantibody levels and synovitis. BAFF level diminished with treatment, along with autoantibody titers, suggesting a rationale to treat ERA patients with BAFF-targeted agents.