Foxp1-deficient CD4 SP and CD8 SP thymocytes have an activated phenotype. (A) Thymic CD4 and CD8 staining profile of 4-week-old Foxp1^f/+Cd4^Cre and Foxp1^f/fCd4^Cre mice. Data are representative of various time points (weeks 4, 5, 8, 10, 21, 22) in at least 4 independent experiments. (B) Total cell numbers of DP, CD4 SP, and CD8 SP thymocytes in Foxp1^f/+Cd4^Cre and Foxp1^f/fCd4^Cre mice at different ages. Data represent average ± SD, weeks 4-5: n = 7, weeks 8-10: n = 7, and weeks 21-22: n = 5. (C) Expression of TCR_β, CD3, CD5, CD44, CD62L, HSA, and Qa-2 in DP, CD4 SP, and CD8 SP thymocytes of 4- to 5-week-old Foxp1^f/+Cd4^Cre and Foxp1^f/fCd4^Cre mice. Data are representative of at least 2 independent experiments.