Supported by grants from the National Institutes of Health (No. K08-HL02621). National Blood Foundation. Lupus Foundation of the Delaware Valley, and the March of Dimes Birth Defects Foundation.
Address for correspondence: Don L. Siegel. Ph.D., M. D., Department of Pathology & Laboratory Medicine, 6–55 Founders Pavilion, Hospital of the University of Pennsylvania, 3400 Spruce Street. Philadelphia, PA 19104.