Inflammatory arthritis induced by single intra-articular injection of lipopolysaccharide (LPS) in transgenic (Tg) mice. One microgram of LPS or 20 μg of zymosan was injected into the knee joints of Tg and wild-type (Wt) mice. Histopathologically, severe synovitis with articular cartilage destruction was observed 2 weeks after injection in Tg mice injected with LPS but not in Tg mice injected with zymosan or phosphate-buffered saline or in Wt mice (×100) (a). The level of tumor necrosis factor-alpha (TNFα) mRNA expressed in inflamed synovia was significantly higher in Tg mice injected with LPS than in Tg mice injected with zymosan or in Wt mice injected with LPS (*P < 0.01) (b). The values are expressed as the mean ± standard deviation for four different mice. GAPDH, glyceraldhyde-3-phosphate dehydrogenase.