CTLA-4 expression in CD34⁺ stem cells and AML and CML neoplastic cells.

(A) Double staining of peripheral blood normal CD34⁺ stem cells and neoplastic cells from AML and CML patients with FITC-conjugated anti–CTLA-4 scFv 83 and PE-conjugated anti-CD33 mAb by flow cytometry. (B) Kinetics of CTLA-4 surface expression after treatment of normal CD34⁺ stem cells and neoplastic cells from AML and CML patients resting or stimulated with GM-CSF. Cells were analyzed by flow cytometry to determine the percentage of positive cells. These results are representative of 3 independent experiments.