1. Section of Glycoconjugate Research, M.R.C. Clinical Research Centre, Watford Road, Harrow, Middx. HAl 3UJ, U.K.
2. Division of Immunology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, U.K.
3. MRC Human Biochemical Genetics Unit, The Galton Laboratory, University College London, Wolfson House, 4 Stephenson Way, London NWI 2HE, U.K.