BBC News' Pallab Ghosh reports on the new treatment

The successful experiment also has important implications for the transplantation of other body tissues, by improving the technology of tissue engineering.

So as well being "the first step towards a cure for baldness", said the transplant donor Dr Colin Jahoda, of the University of Durham, "The results could also be of future benefit in creating replacement skin for burn victims, for example."

The fact that the hair follicle cells were not rejected shows that they have "immune privilege", meaning that hair tissue from complete strangers could be tolerated by transplant recipients. Future tranplant recipients could choose whatever colour and type of hair they wanted.

DNA analysis

Dr Colin Jahoda: "Follicles were gained"

In the experiment, cells from the sheaths of hair follicles were taken from Dr Jahoda's scalp and implanted into the arm of a genetically-unrelated woman - his wife, Dr Amanda Reynolds.

The tissue was not rejected and three weeks after the graft, head hair began to sprout from her arm. All was still well after 77 days.

DNA analysis confirmed it was Dr Jahoda's cells which had caused the hair to grow on Dr Reynold's arm.

"The cells actually instructed and organised her skin cells to grow follicles and make hair," Dr Jahoda told the BBC. He also acknowledged that the idea for the experiment was his wife's: "The actual creative person was Amanda."

Carefully washed

What makes the lack of rejection of the cells remarkable is that Dr Jahoda and Dr Reynolds have different blood groups and incompatible immune systems.

Rejection was avoided by careful washing of the tissue before implantation, so that no blood cells were transferred along with the sheaths.

These are easily identified as foreign by the host body, provoking an immune response and rejection.

Another measure used to reduce rejection was making sure the implantation cuts were as tiny as possible. Wounds to tissue can also provoke immune responses.

However, Dr Jahoda said: "The main reason why the graft was not rejected probably lies with the tissue itself" and its immune privilege.