1. Department of Immunodermatology; St John's Institute of Dermatology; London SE1 9RT U.K
2. Department of Statistics; GSTS and MRC Centre for Transplantation; Guy's Hospital; London SE1 9RT U.K
3. Department of Clinical Transplantation Laboratory; GSTS and MRC Centre for Transplantation; Guy's Hospital; London SE1 9RT U.K