Effects of silencing tumor necrosis factor receptor 1 (TNFR1) in synovial lining cells during streptococcal cell wall (SCW) arthritis. Knee joints of naïve C57BL/6 mice were injected with 107 ffu hairpin construct targeting TNFR1 (HpTNFR1) or hairpin non specific (HpNS), and 2 days post-transduction, joints were challenged with 5 μg of SCW fragments. (a) Expression of indicated genes in synovial tissue at 24 hours after SCW challenge. Data are represented as mean ± standard error of the mean (SEM) (n = 3-6) of the difference in ΔCt values compared with the HpNS group (ΔΔCt). (b) Cytokine protein levels in 1-hour cultures of synovial tissue explants isolated at 24 hours after challenge. Bars represent mean ± SEM (n = 7), and statistical differences were determined using Student t test. *P < 0.05. Ct, cycle threshold; IL, interleukin; TNF, tumor necrosis factor.