IL-10 receptor dominant-negative transgenic mice were highly susceptible to collagen-induced arthritis (CIA). (A) Sex- and age-matched DBA/1J transgenic (Tg) and wild-type (Wt) littermate control mice were immunized with bovine type II collagen as described in "Materials and methods." The clinical arthritis score was observed, scored and recoded daily. Left (Wt males, n = 10, Tg males, n = 9; P > 0.05). Right (Wt females, n = 12, Tg females, n = 13; P < 0.01). The results of one of three repeated experiments are shown. (B) Representative H & E-stained sections of paw joints from Wt and Tg mice on day 50 postimmunization in CIA animals are shown (original magnification, ×10; scale bar, 100 μm). (C) Histological scores of paw joints on day 50 postimmunization. Each feature of arthritis (joint space exudate, synovitis, pannus formation and cartilage and bone degradation) was graded from 0 (normal) to 5 (severe). The values given are means and SEM (n = 4 per group; females, P < 0.01, and males, P > 0.05). The results are representative of two experiments.