IFN-α production in PBMCs stimulated using serum from SLE patients or healthy control individuals. (a) Peripheral blood mononuclear cells (PBMCs), obtained from healthy individuals, were incubated with serum from patients with systemic lupus erythematosus (SLE) or healthy control individuals for 24 hours. Interferon (IFN)-α production was measured using ELISA. The solid bars represent the mean value for each experimental group. The experiment was performed twice using PBMCs obtained from separate healthy individuals. Data are representative of two independent experiments. (b) Inverse correlation between the amount of CpG induced IFN-α production in SLE PBMCs (n = 22) versus SLE serum induced IFN-α in control PBMCs. (c) Positive correlation between the amounts of immune complexes versus SLE serum induced IFN-α in control PBMCs (n = 14). (d) Inverse correlation between the amount of CpG-induced IFN-α production in SLE PBMCs versus the amounts of immune complexes (n = 14). Correlation analyses were performed using Spearman's rank correlation test.