1. Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
2. Immunobiology and Transplantation Department, Naval Medical Research Institute, Bethesda, MD 20814.
3. Department of Pathology, George Washington University School of Medicine, Washington, DC 20037.
4. Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.