1 Orthopedic Section, Office of the Clinical Director, Intramural Research Program, National Institute of Arthritis and Musculoskeletal and Skin Disease, National Institutes of Health, Department of Health and Human Resources, Bethesda, MD.2 Transplantation Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Resources, Bethesda, MD.3 Department of Dermatology, Johns Hopkins Medical Institutions, Baltimore, MD.4 Department of Pathology, University of Miami, Miami, FL.5 Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Department of Health and Human Resources, Bethesda, MD.