1. Transplantation and Autoimmunity Branch, National Institute of Diabetes, Digestive and Kidney Diseases (A.S., S.C.H., B.H., D.M.H.), National Institutes of Health, Bethesda, Maryland 20889-5603
2. Basic Research Laboratory, National Cancer Institute (C.A.P., M.R., J.N.B.) National Institutes of Health, Bethesda, Maryland 20889-5603