Stem Cell Research, Nuffield Division of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK, NHS Blood and Transplant Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.|Stem Cell Research, Nuffield Division of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK, NHS Blood and Transplant Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.|Department of Drug Science and.|Department of Mathematics and Computer Science, University of Catania, 95125 Catania, Italy.|Department of Mathematics and Computer Science, University of Catania, 95125 Catania, Italy.|Department of Drug Science and.|Stem Cell Research, Nuffield Division of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK, NHS Blood and Transplant Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.