Low-dose plasmid DNA inhibits production of IL-6 and TNF-α by LPS-stimulated macrophage cell line. J774 cells were stimulated with pcDNA3 at different concentrations in the absence (A) or presence of 0.5 μg/mL of LPS (B and C). After 48 h, the concentrations of IL-6 (A and B) and TNF-α (C) were determined in the culture supernatants. Assays were performed in triplicate and the results represent the mean ± SD of at least three independent experiments. *, P < 0.05 versus group stimulated with LPS only.