1 The Jenner Institute, Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), University of Oxford, Oxford OX1 2JD, UK.
2 Immunology, RIA, Inselspital, University of Bern, 3010 Bern, Switzerland.
3 Artemis Bio-Support, Molengraaffsingel, 2629 Delft, The Netherlands.
4 Department of Chemistry and Biochemistry, University of Bern, 3010 Bern, Switzerland.