Increased levels of BAFF in patients with Systemic Lupus Erythematosus are associated with acute phase reactants, independent of BAFF genetics: a case control study

Abstract

Objectives. To determine whether increased levels of B-cell activating factor (BAFF) in patients with SLE are due to disease activity or genetic variations in the promoter region of the BAFF gene and BAFF gene expression. Methods. The case-control study included 101 SLE patients and 111 healthy controls. Five single nucleotide polymorphisms (SNPs) in the BAFF promoter region were investigated by melting point analysis: c.-2841 (T > C), c.-2704 (T > C), c.-2701 (A > T), c.-871 (C > T) and c.-514 (A > G). BAFF mRNA levels were determined by real-time PCR (BAFF-RQ) and serum BAFF (s-BAFF) levels were measured by ELISA. Independent predictors that might be correlated with increased s-BAFF in SLE patients were analysed by multivariate regression methods. Results. Although s-BAFF levels were increased in SLE patients (1.73 vs 0.98 ng/μl, P < 0.001), no specific BAFF genotype was found to associate with SLE. The different genotypes defined by the investigated SNPs were identified both in SLE patients and healthy controls with similar frequencies. No association was found between BAFF genotype and BAFF-RQ. s-BAFF was independent of other factors, correlated with CRP (β = 0.40, P < 0.001) and physician's visual analogue score (R = 0.21, P = 0.046) and inversely with haemoglobin (β = -0.32, P < 0.001) and IgA (β = -0.33, P = 0.001). Conclusions. Increased s-BAFF levels in SLE patients are associated with the acute-phase responses, CRP and haemoglobin, but probably not dependent on BAFF genotype or expression. This indicates that s-BAFF production occurs at sites of inflammation.