Development of collagen-induced arthritis is independent of the source of collagen type II. (a) Body weight changes over time are expressed as the percentage of weight relative to day 0 (blue line), and clinical signs were analyzed twice a week and summarized in an Integrated Discomfort Score (red line). The number of affected joints (aj) involved in the arthritis is indicated above the dashed line. Group I was immunized with chicken-origin collagen type II (ch-CII): M03136, M05031*, M05041, M04031*, M04111* and M04121. Group II was immunized with bovine-origin collagen type II: M03137*, M05032, M05042, M05003, M05026* and M05038*. Animals were boosted on day 35 if they did not develop clinical arthritis at day 28 (black triangles). The upper two lines of graphs are twin siblings (green accolade). *Sacrificed just after the onset of clinical disease. (b) ch-CII reproducibly induces collagen-induced arthritis (CIA) with high incidence but variable disease course. PID, post induction day.