Adam J Mead PhD, FRCP, FRCPath, FMedSci Haematopoietic Stem Cell Biology Laboratory, Medical Research Council Molecular Haematology Unit, Medical Research Council Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK Michael A Laffan DM, MRCP, FRCPath Department of Immunology and Inflammation, Faculty of Medicine, Imperial College London, London, UK Graham P Collins DPhil, FRCP, FRCPath Department of Haematology, Oxford Cancer and Haematology Centre, Oxford, UK Deborah Hay DPhil, MRCP, FRCPath Nuffield Division of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford, Oxford, UK Consulting Editor A Victor Hoffbrand MA, DM, FRCP, FRCPath, FRCP (Edin), DSc, FMedSci Emeritus Professor of Haematology, University College London, London, UK Honorary Consultant Haematologist, Royal Free Hospital, London, UK