CD8⁺ T cell tolerance in Tie2-LacZ mice. Tie2-LacZ mice were crossed with TCR-trangenic Bg1 mice. Thymocytes from Tie2-LacZ (T2; top row), Bg1 (middle row), and Bg1 × Tie2-LacZ mice (Bg1 × T2; bottom row) were stained for CD4 and CD8 expression. The expression of the transgenic Vβ7 chain and binding of the H2-K^b-β-gal_96-103 tetramer was determined by gating on CD8⁺ T cells. Values in the top right quadrants indicate mean frequencies of CD4/CD8-positive cells in thymocytes or percentage of antigen-specific cells in single CD8⁺ thymocytes, respectively (T2, n = 2; Bg1, n = 3; Bg1 × T2, n = 7). Splenocytes were assessed for Vβ7 and CD8 expression. Percentage of β-gal_96-103–specific cells was determined by Vβ7 and H2-K^b-β-gal_96-103 tetramer staining, gating on CD8⁺ T cells (T2, n = 3; Bg1, n = 5; Bg1 × T2, n = 9).