Intracellular localization of CTLA-4 in activated CD34⁺ stem cells and AML neoplastic cells.

(A) Immunostaining with the biotin-conjugated anti–CTLA-4 scFv67 and AP-labeled streptavidin of neoplastic cells from peripheral blood of an AML patient. (B) Immunostaining with the anti–CTLA-4 BN13 mAb and AP-labeled antimouse immunoglobulin antibody of CD34⁺ stem cells activated with GM-CSF for 7 days. Staining was performed on cytospins, visualized by the addition of phosphatase substrate, and counterstained by hematoxylin (original magnifications: panel A, × 70; panel B, × 110). Panel A and B stainings show cytoplasmic and membrane positivity for CTLA-4.