1. Kennedy Institute of Rheumatology, University of Oxford, Oxford OX3 7FY, U.K.
2. Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, U.K.
3. School of Clinical Medicine, University of Cambridge, Cambridge CB2 0SP, U.K.
4. The Jenner Institute, University of Oxford, Oxford OX3 7DQ, U.K.