1. From the Departments of Immunology (P.I.H., P.D.M., R.J.B., M.H.-F., L.F., G.L., L.W., R.B., R.I.L.) and Cardiothoracic Surgery (P.I.H., K.T.), Imperial College School of Medicine, Hammersmith Hospital, London, and Department of Cardiothoracic Surgery (M.L.R., M.H.Y.), Harefield Hospital, Middlesex, UK.