1. Division of Parasitology MRC National Institute for Medical Research London NW7 1AA UK
2. Division of Molecular Immunology MRC National Institute for Medical Research London NW7 1AA UK
3. Institute of Immunology and Infection Research Centre for Immunity Infection and Evolution School of Biological Sciences University of Edinburgh Edinburgh EH9 3JT UK
4. Mary Lyons Centre MRC Harwell Oxfordshire OX11 0RD UK