1. ARC Epidemiology Research Unit, Stopford Building, Oxford Road, Manchester M13 9PT, UK,,
2. National Blood Service, North London Centre, Colindale Avenue, London NW9 5BG, UK,,
3. Tissue Typing Laboratory, The Royal London Hospital, 55–76 Ashfield Street, Whitechapel, London E1 1BB, UK.
4. Immunology Group, School of Biological Sciences, Stopford Building, Oxford Road, Manchester M13 9PT, UK, and,