XENOTRANSPLANTS - animal to human transplants - have won ethical approval after the Nuffield Council on Bioethics, set up to debate medical morality, gave its go-ahead. However, while xenotransplants are in principle an ethical way of dealing with the shortage of human organs for transplant, one "should proceed with caution, always paying attention to the highest standards of patient care and animal welfare", said Albert Weale, who headed the council's working party.

Nuffield began its debate after advances in the field pioneered by Imutran, a Cambridge-based biotech company, reached great heights. Imutran, set up in 1984, has bred trangenic human pigs containing a human protein that regulates part of the immune resonse. Hearts from these pigs have been transplanted in monkeys with moderate success. Human trials are to begin shortly.