Cell surface phenotypic characterization of TEL-JAK2 leukemic cells by flow cytometry. (A) Cell surface immunostaining of 3 representative TEL-JAK2 tumor cases (nos. 31, 35, and 58) using antibodies against CD3ϵ, TCRβ, CD24, and CD25. Leukemic cells were also stained with an isotypic control monoclonal antibody. CD3ϵ and TCRβ expression in normal CD8 SP thymocytes is also shown. (B) Leukemic cells from 2 representative TEL-JAK2 transgenic tumors (nos. 1115 and 1281) were stained with CD62L or an isotypic control antibody. (C) CD5 expression levels in CD4/CD8 DP, CD4 (CD4SP), and CD8 (CD8SP) wild-type thymocytes as compared to isotypic antibody-labeled thymocytes (top panel). Leukemic cells from 2 representative TEL-JAK2 transgenic tumors (nos. 1119 and 1129) were stained with CD5 or an isotypic control antibody (bottom panel). (D) Wild-type thymocytes (WT) and 3 representative TEL-JAK2 transgenic tumors (nos. 1531, 1551, and 1563) were double-stained with CD25 and CD122 antibodies. Cell percentages for each quadrant are indicated.