Disease severity in DR1-T cell receptor (TCR) Tg mice (panels A and B). The severity (panel A) and percentage of arthritic limbs (panel B) of disease in double-transgenic mice (squares, n = 13) compared with DR1 Tg littermate controls (diamonds, n = 15). All animals were challenged with a dose of 100 μg of bovine type II collagen (bCII) emulsified in CFA (Complete Freund’s Adjuvant) for the induction of disease. Mice were scored for arthritis severity as described in Methods. Panel A, P = 0.009 on day 55 when comparing the mean severity scores ± standard error of the mean using the Mann–Whitney test; panel B, P = 0.002 on day 55 when comparing the number of arthritic limbs using Fischer’s exact test. The final incidence was 70% for the single-transgenic mice and 90% for the double-transgenic mice. Histology of joints of arthritic animals (panel C): left, joint from double-transgenic animal showing more eroding pannus and greater amounts of damaged articular cartilage compared to a representative joint (right), from a single-transgenic animal. The animals were sacrificed eight weeks after immunization. Joints were collected, fixed with formaldehyde, and decalcified prior to staining with H&E. The tissues were photographed using an inverted-phase contrast microscope (original magnification: 50×). The data shown are representative of data obtained by analyzing numerous sections from hindpaws taken from 6 animals per group.