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

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).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).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.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.