Andrew E Armitage1, Hal Drakesmith2. 1. MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK. 2. MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK. alexander.drakesmith@ndm.ox.ac.uk.