Circulating interferon-α2 levels are increased in the majority of patients with systemic lupus erythematosus and are associated with disease activity and multiple cytokine activation

Mutations in interferon (IFN) regulatory factor genes and the biological activity of type I IFN on expression of specific genes that are induced by IFN have been associated with various aspects of systemic lupus erythematosus (SLE). Circulating levels of IFN-α in SLE has not been extensively studied because of limited sensitivity of available ELISA assays. We performed a cross-sectional case-control study where circulating levels of IFN-α2 were measured by a highly sensitive, solution phase multiplex magnetized bead assay and investigated the relation of IFN-α2 with autoantibody profiles, clinical disease activity and levels of inflammatory cytokines in SLE patients (n = 87). Cytokine levels were determined on stored sera aliquots with cut-off levels determined by the geometric mean + 2SD in healthy controls (n = 27). IFN-α2 levels were increased in 64% of SLE patients, who displayed more renal disease and higher disease activity (p = 0.06) and had a significantly higher sum of activated cytokines (median...