Accumulation of CD4SP cells with a developmentally intermediate phenotype in DN-IkTg thymocytes. (A) Maturation marker expression on CD4SP cells from WT and DN-IkTg thymocytes. Cell surface expression of indicated surface proteins were assessed for WT (open histogram) and DN-IkTg (shaded histogram) cells and overlaid with control Ab staining (dotted line). Data are representative of 13 independent experiments with at least 10 WT and 13 DN-IkTg mice. (B) Developmental arrest in DN-IkTg thymocytes. Contour plots show HSA vs surface TCRβ expression on total thymocytes (left). Box I identifies HSA^hiTCRβ^hi immature thymocytes, which underwent positive selection. Box II indicates HSA^loTCRβ^hi mature postselection thymocytes. CD4 vs CD8 profiles of box I or box II gated thymocytes are shown on the right. Contour plots are representative of 8 independent experiments that analyzed 10 WT and 13 DN-IkTg mice. (C) RORγt expression in RORγt-EGFP.DN-IkTg mouse thymocytes. RORγt transcription (EGFP expression) was assessed in the indicated cell populations of DN-IkTg mice expressing an RORγt-EGFP reporter allele. The histogram is representative of 3 independent experiments with 5 RORγt-EGFP and 9 RORγt-EGFP.DN-IkTg mice. (D) Surface CD8α levels on mature HSA^loCD3^hi CD8SP thymocytes. The histogram is representative, and the bar graph shows the mean ± SEM, of 7 independent experiments with each 1 WT and 1 DN-IkTg mouse.