Development of a double-transgenic DR1-T cell receptor (TCR) Tg mouse model of autoimmune arthritis. The double-transgenic DR1-TCR Tg mouse model was developed and backcrossed onto DR1 transgenic mice as described in Methods. To detect the presence of the transgene, spleen cells were stained with a combination of anti-Vβ8- fluorescein isothiocyanate (FITC) and anti- TCR-phycoerythrin (PE). (A) Representative data obtained from the single-transgenic DR1 mouse; (B) representative data obtained from the double-transgenic mouse. In a similar manner, peripheral blood cells were obtained from the single-transgenic DR1 mouse (C) and compared to cells from the double-transgenic mouse (D), staining with antibodies specific for CD4+, Vβ8.1 and Vα2. The majority of the CD4+ cells in the double-transgenic mouse express both Vβ8.1 and Vα2. Data are based on the analysis of 10,000 gated events with the gate set on forward versus side scatter to exclude non-lymphoid cells and dead cells.