Thymocyte developmental arrest in tal-1/scl and muttal-1 transgenic mice. (A) Total thymocyte cell numbers from 4-week-old wild-type and tal-1/+, tal-1/tal-1, and mut tal-1/+ transgenic mice. (B) Tal-1 transgenic mice have reduced numbers of DP and CD4⁺cells. The absolute numbers of DP (▪) and CD4⁺ (▨) cells in wild-type, tal-1/+, tal-1/tal-1, and mut tal-1/+ 4-week-old mice are plotted. Error bars indicate variability from animal to animal. (C) Tal-1 expression perturbs thymocyte development. Thymocytes from 4-week-old wild-type, tal-1/+, tal-1/tal-1, and mut tal-1/+ transgenic mice were stained with CD4-Cy and CD8-FITC and analyzed by flow cytometry. (D) Tal-1/scl expression in the thymus blocks the progression of cells through the stages of double-negative development. Cells were stained with antibodies for the lineage markers IgM, Ter119, Gr1, Mac1, PanNK, CD3, CD4, and CD8 as well as CD25-PE and CD44-FITC. The staining of lineage-negative cells with CD25-PE and CD44-FITC is shown. Numbers in quadrants represent percent of cells stained with antibodies.