A team of researchers involving scientists from the Czech Republic has discovered that one type of blood cell, hitherto thought to be harmless, can reduce the success of a bone marrow transplant: so-called NK cells (natural killer cells) present in the donor sample can weaken haematopoietic stem cells . The research was conducted by an international team led by Meritxell Alberich-Jordová from the Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic.