Preserved development of αβ lineage T cells in the absence of Maml1. (A) Flow cytometric analysis showed a similar percentage of CD4⁺CD8⁺ double-positive and CD4⁺ or CD8⁺ single-positive thymocytes in recipients of Maml1^−/− compared with Maml1^+/− progenitors. Numbers indicate the percentage of cells in each quadrant. Host-derived CD45.1⁺ cells were excluded from the analysis. (B) Normal distribution of Lin⁻ thymocyte progenitor subsets, as defined using c-Kit and CD25 expression, in recipients of Maml1^−/− compared with Maml1^+/− progenitors. Numbers indicate the percentage of cells in each quadrant. Host-derived CD45.1⁺ cells were excluded from the analysis. (C) Absolute number of donor-derived double-positive thymocytes in all the fetal liver chimeras that were analyzed (Maml1^+/−, ▵, n = 21; Maml1^−/−, ▴, n = 9). The trend for decreased numbers of double-positive thymocytes in Maml1^−/− compared with Maml1^+/− progenitors was not statistically significant (P = .14; Student t test).