LEUKAEMIA affects thousands of children all over the world, accounting for over a third of all cancers diagnosed for children. The bone marrow tissue, which produces blood cells, churn out faulty products in these kids.

The only option is replacement of the marrow. But replacement of bone marrow requires a donor with matching protein molecules, called human leucocyte antigens (HLA), which sit on the surface of marrow cells. Also, for successful transplantation, at least four of the six hlas should match between the donor and the recipient, otherwise the tissue is promptly rejected by the recipient.

And to compound the problems, hlas are among the most variable proteins known. Therefore, the report of the teams of Joanne Kurtzberg of Durham's Duke University Medical Centre, and Pablo Rubinstein of New York Blood Centre that an entirely new strategy can be followed to save these kids using placental blood has been welcomed widely. They have successfully treated 25 patients, including a variety of non-malignant and malignant conditions (nejm, Vol 335, No 3). The strategy of this team has been to develop an alternate source of cells known as blood stem cells.

Blood stem cells are very difficult to isolate and use for transplantation purposes. While these occur in the marrow, another important source has been overlooked until recently