1. Department of Surgery, University of Edinburgh Medical School, Teviot Place, Edinburgh EHS 9AG, UK
2. SNBTS Protein Fractionation Centre, Ellen's Glen Road, Edinburgh EH17 7QT, UK
3. National Institute for Biological Standardisation and Control, Potters Bar EN6 3QG, UK
4. Department of Immunology, University of Birmingham, Birmingham B15 2TG, UK