Immunophenotypic heterogeneity among mouse Tal1/Lmo2 tumors. (A) Wild-type thymocytes and 25 Tal1/Lmo2 tumors were stained with CD4 and CD8 antibodies, and the lineage-negative tumor cells were stained with CD25 and CD44 antibodies and analyzed by flow cytometry. Four representative Tal1/Lmo2 tumors are shown. Gating is based on the wild-type control stained with each individual tumor. (B) Tumor-associated thymic progenitors are maintained on transplant. Tal1/Lmo2 tumor cells were then injected via subcutaneous injection into recipient mice. At death, the immunophenotype of the transplanted tumor was reanalyzed by flow cytometry and compared with the primary tumor. Five tumors were analyzed; one representative tumor is shown.