1. From the Departments of Medicine (D.C.K., X.Y., E.P., S.H., S.S., B.S., L.O.), Cell Biology (E.P.), Microbiology and Immunology (M.W.C.), University of Oklahoma Health Sciences Center and VA Medical Center, Oklahoma City; and McAlester Clinic (J.M.), McAlester, Okla. Current address (L.O.): The Cleveland Clinic, Ohio.