Gal-1 promoted agonist-driven negative selection of CD8⁺ T cells in male H-Y TCR transgenic mice. (A) CD8 versus CD4 expression profiles of thymocytes from wild-type (middle) and gal-1^−/− (right) male H-Y TCR transgenic mice and a wild-type female H-Y mouse (left) processed in parallel. The percentage and total number of thymocytes are shown in the boxed region and represent the DP and CD8⁺ SP populations. (B) Flow cytometric histograms of CD3 staining of DP (thin line) and CD8⁺ SP (thick line) thymocytes from a control wild-type female H-Y mouse and CD8⁺ SP thymocytes from a gal-1^−/− male H-Y mouse (shaded). (C, D) The total number of DP/CD8⁺ SP (C) and CD8⁺ SP (D) thymocytes from wild-type (n = 4) and gal-1^−/− (n = 5) male H-Y TCR mice. These populations were determined by setting quadrants based on a wild-type female H-Y TCR control (Figure 4A). Each point represents one mouse, and total cell number was determined as described in Figure 3C over the course of 4 independent experiments. The horizontal bar represents the mean. (E) CD8 versus CD4 expression profiles of splenic cells from wild-type (left) and gal-1^−/− (right) male H-Y TCR mice. The percentage of cells in each subset is shown in its respective quadrant. (F) Flow histogram of CD3 staining of CD8⁺ T cells from wild-type (shaded) and gal-1^−/− (thin line) mice. (G) The total number of CD8⁺ T cells from spleens of wild-type (n = 4) and gal-1^−/− (n = 5) male H-Y TCR mice. The total number of CD8⁺ T cells was determined as described in Figure 3, and each point represents one mouse over the course of 4 independent experiments. All flow profiles are representative of 4 independent experiments. For panels C, D, and G, 2-tailed unpaired Student t tests were performed to determine statistical significance. P values are listed in the panels.