mRNA expression of STAT-1, STAT-3, interferon regulatory factor (IRF)-1 and CD40 in murine arthritic knee joints. Total RNA was isolated from joint capsules including the synovial tissue before (day 0) and after (day 1 to day 21) arthritis induction (n = 5 for day 0, 1, 3 and 7; n = 4 for day 14 and 21). After reverse transcription, mRNA expression of STAT-1, STAT-3, IRF-1 and CD40 was measured by real time PCR. The house keeping genes encoding β-actin (for STAT-1 and STAT-3) and GAPDH (for IRF-1 and CD40) were used for normalization of expression. Mean of day 0 expression was set at 100%. *P ≤ 0.05, **P ≤ 0.01 versus day 0.