1. Section of Paediatrics, Imperial College, Norfolk Place, London W2 1PG, UK.
2. Immune Regulation Section, Laboratory of Malaria Immunology and Vaccinology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Twinbrook II Room 239 A, 12441 Parklawn Drive, Rockville, MD 20852, USA.
3. Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.