C1q inhibits expression of HMGB1-induced IFN-α, MX1, and inflammatory cytokines by human monocytes. (A) Messenger RNA (mRNA) levels for IFN-α, MX1, IL-6, and TNF-α in monocytes stimulated with or without HMGB1 (3 μg/mL) and various concentrations of C1q (μg/mL) for 6 hours in serum-free medium (mean ± standard deviation [SD] of triplicates, N = 3). (B) HMGB1 (3 μg/mL) -induced IL-6 and TNF-α secretion were reduced in the presence of various concentrations of C1q, assessed at 24 hours (mean ± SD of duplicates, N = 3). (C) IFN-α, MX1, IL-6, and TNF-α mRNA expression by monocytes transfected with control siRNA or LAIR siRNA and treated with C1q (25 μg/mL), HMGB1 (3 μg/mL) for 6 hours (mean ± SD of triplicates, N = 3). Data are expressed as fold induction relative to controls. R.E., relative expression. ns, not significant. *P < .05; **P < .01; ***P < .001 (one-way ANOVA with Bonferroni’s correction for multiple comparisons).