1 Sickle Cell Vascular Disease Section, Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD.
2 Flow Cytometry Core Facility, National Heart, Lung, and Blood Institute, Bethesda, MD.
3 Electron Microscopy Core Facility, National Heart, Lung, and Blood Institute, Bethesda, MD.
4 Department of Medicine, Division of Hematology-Oncology, Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA.