1. School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15
2TT, U.K.
2. School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15
2TT, U.K.
3. Medical Research
Council Human
Immunology Unit, Nuffield Department of Medicine, Weatherall Institute
of Molecular Medicine, University of Oxford, Oxford OX3 9DS, U.K.