Therapeutic cloning

Transplanting stem cells

Adult stem celltransplants use a patient's own stem cells. The cells are therefore genetically identical to the patient's cells and so will not be rejected by the patient's immune system.

If this is not possible, then the stem cells have to come from a donor. There are fewer complications if the stem cells come from a close member of the family. Alternatively, donor cells can come from a person with closely matched tissue types.

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Embryonic stem cells will always come from a donor - unless stem cells were collected from the patient when they were an embryo.

Therapeutic cloning

Therapeutic cloning could produce stem cells with the same genetic make-up as the patient.

The technique involves the transfer of the nucleus from a body cell of the patient, to a human donor egg cell whose nucleus has been removed.

Diagram illustrating the process of using a donor egg cell in order to obtain stem cells

Stem cells produced in this way could be transferred to the patient. Although human stem cells have been produced in this way, and used in research, there is no evidence that, as yet, they have been used to treat anyone.