‘Natural killer’ cells in the new bone marrow then attack the leukemia, says Professor Andrea Velardi, from the University of Perugia in Italy.

Bone marrow transplantation has been around for a long time, and, in leukemia, it is traditionally given to patients to replace bone marrow destroyed by powerful anti-cancer treatments.

However, one of the biggest problems in bone marrow transplantation is when the immune cells in the donated bone marrow ‘reject’ their new host.

They launch attacks, which can prove fatal in the worst cases, a condition called ‘graft versus host disease’.

To avoid this, patients and donors are carefully screened to produce as perfect a match as possible.

However, some of the most recent research in bone marrow transplantation focuses on using the disease-fighting qualities of bone marrow to destroy cancer cells, either to prevent the disease coming back or to tackle it head-on, even where it is resistant to drugs and other treatments.

Professor Velardi is looking for ways to harness these qualities without raising the risk of graft versus host disease.

He has been using donors from the patient's own family who are only a partial match - sharing only 50percent of their genetic material.