Effect of mAb C11C1 on HLA-B27 transgenic rat inflammatory arthritis. (a) Effects of monoclonal antibody (mAb) C11C1 on clinical signs of arthritis in human leukocyte antigen B27 (HLA-B27) rats. mAb C11C1 was administered at the same dose and frequency as in Fig. 2a. Mean joint score was determined daily, except at weekends. All joint scores are significantly different between the two groups for each corresponding day (P < 0.001) except for days 1 (P > 0.03), 2 (P = 0.01) and 3 (P = 0.006). Data are shown as means ± SEM. Filled circles, IgG1-treated group; open circles, mAb C11C1-treated group. (b) Effects of mAb C11C1 on joint histology in HLA-B27 rats. Photomicrographs of representative sections of tarsal joints from C11C1-treated (left) and IgG-treated (right) HLA-B27 transgenic rats. Note the clear joint space (a) and normal appearance of bone (b) in the mAb C11C1-treated group (left) compared with the inflamed villus formation (arrows) occupying the synovial space (a) in the IgG-treated group (right). Hematoxylin and eosin stain; original magnification × 100. (c) Effects of mAb C11C1 on synovial inflammatory changes in HLA-B27 rats. Treatment with mAb C11C1 (open bars) decreased synovial proliferation (hyperplasia) (P = 0.01), subsynovial fibrosis (fibroplasia) (P = 0.001), and degree of inflammation (P < 0.001), but not pannus formation. The total score of the control IgG1 of 9.6 ± 1.0 was reduced by mAb C11C1 to an inflammatory score of 5.0 ± 1.0 (P = 0.009). Data are shown as means ± SEM. *P < 0.05; **P < 0.01; ***P < 0.005. (d) Effects of mAb C11C1 on cartilage and bone inflammatory changes in HLA-B27 rats. mAb C11C1 (open bars) significantly improved (decreased the Mankin score of) the cartilage organization (P = 0.01) and the altered chondrocyte proliferation (P = 0.008). The proteoglycan cartilage contents (Safranin O/Fast Green staining) were similar in both experimental groups (P > 0.05) and the tidemark integrity was preserved (data not shown). The total Mankin score was significantly decreased in the mAb C11C1-treated group (P = 0.02). Data are shown as means ± SEM. *P < 0.05; **P < 0.01; ***P < 0.005.