Immunohistochemic staining of bone marrow sections.

Microvascular endothelial cells were highlighted by antibodies against thrombomodulin (A,C). VEGFR-2–positive leukemic blasts were identified by anti–VEGFR-2 antibodies (B,D). Immunohistochemic localization was performed by the alkaline phosphatase/anti–alkaline phosphatase bridge technique (Dako-APAAP Kit). A and B denote bone marrow samples obtained before; C and D, 8 weeks after treatment with SU5416. Original magnification, ×500.