1 NHS Blood and Transplant Centre, John Radcliffe Hospital, Oxford OX3 9BQ, UK; Oxford National Institute for Health Research Biomedical Research Centre, Oxford University Hospitals, University of Oxford, Oxford, UK. Electronic address: mike.murphy@nhsbt.nhs.uk.
2 NHS Blood and Transplant Centre, John Radcliffe Hospital, Oxford OX3 9BQ, UK; Oxford National Institute for Health Research Biomedical Research Centre, Oxford University Hospitals, University of Oxford, Oxford, UK.
3 Department of Pathology and Department of Medicine (Hematology), Stanford University, Stanford, CA, USA.