Central deletion of autoreactive T cells is mediated by retrovirally encoded MHC class II β chain. Eleven weeks after bone marrow transplantation, NOD mice reconstituted with either MMP-IAβ-d-GFP_ or control MMP-GFP_transduced bone marrow were sacrificed, and single-cell thymocyte suspensions were prepared. Single-cell suspensions were also prepared from naive age-matched NOD and BALB/c control mice. Thymocytes were stained with anti-CD4 and anti-CD8 antibodies, annexin V, and I-A^g7 tetramers loaded with either the control CLIP peptide or BDC-15 peptide, and analyzed by flow cytometry. (A) Single-positive CD4 T cells from mice reconstituted with bone marrow transduced with MMP-IAβ-d-GFP do not bind I-A^g7/BDC-15 tetramers. Cells were gated on live annexin V^_CD4⁺CD8^_ single-positive CD4 T cells. The percentage of these cells that bound to I-A^g7/CLIP (top row) and I-A^g7/BDC-15 tetramers (bottom row) is shown in the upper right quadrant. Shown is 1 representative experiment of 3. (B) Specific deletion of I-A^g7/BDC-15_binding T cells in mice reconstituted with bone marrow transduced with MMP-IAβ-d-GFP. Shown is expression of CD4 and CD8 after gating on I-A^g7/BDC-15 tetramer⁺, annexin V^_ (live) cells. The total number of CD4⁺ single-positive T cells that bound the I-A^g7/BDC-15 tetramer was calculated by multiplication of the frequency of these cells by the total number of thymocytes recovered and is shown in the upper left quadrant. The total number of CD4⁺CD8⁺ double-positive thymocytes that bound the I-A^g7/BDC-15 tetramer was calculated similarly and is shown in the upper right quadrant. One representative experiment of 3 is shown.