TLR4-mediated IL-12 production by joint cells promotes antibody-induced arthritis. To induce antibody-induced arthritis, mice were injected with K/BxN serum (100 μL) twice (A, B, D, E). (A) interferon (IFN)-γ, transforming growth factor (TGF)-β, interleukin(IL)-12p35, IL-1β, and IL-6 transcript levels were measured in the joints of wild type and TLR4-/- mice, which had been injected with lipopolysaccharide (LPS), 10 days after serum injection (100 μL of serum, twice) by real-time PCR (n = 4). LPS (5 μg/300 μL in phosphate-buffered saline (PBS)) was injected intraperotineally (i.p.) one day prior to K/BxN serum transfer. (B) STAT4 and phospho-STAT4 expression in joint cells from WT mice, some of which had been injected with LPS, as analyzed by Western blotting. (C) Joint cells from WT mice with arthritis were incubated with LPS and a control peptide, MyD88 or TRIF inhibitor, and IL-12 levels were measured in culture fractions. (D) Ankle thickness and clinical scores were measured in WT and IL-12p35-/- mice, some of which had been injected with LPS (5 μg in 300 μL of PBS) in the K/BxN serum transfer model (n = 6). (E) IL-4, IFN-γ, TGF-β, IL-12p35, IL-1β and IL-6 transcript levels were measured in the joints of WT and IL-12p35-/- mice, some of which had been injected with LPS (5 μg in 300 μL of PBS) 10 days after K/BxN serum transfer by real-time PCR (n = 6). The results shown are representative of three repeated independent experiments. n.s., not significant; * P < 0.05, ** P < 0.01, *** P < 0.001.
Kim and Chung Arthritis Research & Therapy 2012 14:R210 doi:10.1186/ar4048