Lack of CTLA-4 expression in pmel-1 CTLA-4^–/– mice results in dysregulation of CD4⁺ T cells. (A) CD4⁺ T-cell population is overrepresented in pmel-1 CTLA-4^–/– mice. Flow cytometry for CD4 and CD8 expression on splenocytes from pmel-1 CTLA^+/+ and pmel-1 CTLA-4^–/– mice. Results are shown after lymphocyte gating and are representative of 2 independent experiments. (B) Lack of CTLA-4 expression in pmel-1 CTLA-4^–/– results in dysregulation of the CD4⁺ TCR repertoire. Flow cytometry for CD4 and Vβ13 expression on splenocytes from pmel-1 CTLA^+/+ and pmel-1 CTLA-4^–/– mice. Results are shown after lymphocyte gating.