Effect of mAb C11C1 on HLA-B27 transgenic rats colonic inflammation. (a) Effects of monoclonal antibody (mAb) C11C1 on diarrhea in human leukocyte antigen B27 (HLA-B27) rats. Stool score was determined five times a week (normal stool = 1, soft stool = 2, watery stool = 3). mAb C11C1 (1.9 mg/kg) was administered three times a week for 16 days. The control group received murine isotype IgG1 (6 mg/kg) three times a week for 16 days. All stool scores are significantly different between the two groups for each corresponding day (P < 0.005) except for day 11 (P = 0.03). Data are shown as means ± SEM. Filled circles, IgG1-treated group; open circles, mAb C11C1-treated group. (b) Effects of mAb C11C1 on colonic mucosa in HLA-B27 rats. Photomicrographs of representative sections of colon from C11C1-treated (left) and IgG-treated (right) HLA-B27 transgenic rats. Note the extensive inflammatory cell infiltrates within the mucosa (a) and submucosa (b) with loss of villus formation on the mucosal surface indicated by the arrow (a) in the IgG group (right) compared with the C11C1 group (left). The branched arrow (left) points to the villus formation normally present in the colon (mAb C11C1-treated group). Hematoxylin and eosin stain; original magnification × 100. (c) Effects of mAb C11C1 on colonic inflammatory changes in HLA-B27 rats. mAb C11C1 decreased inflammatory changes in the colonic sections as evaluated by ulceration (P = 0.02), inflammation (P < 0.001), depth of lesion (P = 0.004), and degree of fibrosis replacement (P = 0.01) compared with IgG1 administration. Treatment with mAb C11C1 (open bars) significantly decreased the extent and intensity of the total colonic inflammatory score (P = 0.004). Data are shown as means ± SEM. *P < 0.05; ***P < 0.005.