1. Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K., Rega Institute for Medical Research, Laboratory of Immunobiology, University of Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium, Department of Surgery, Royal Free and University College London Medical School, 67-73 Riding House Street, London W1W 1EJ, U.K., and Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, U.K.