The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say, which was which. --George Orwell, Animal Farm George Orwell's vision will come one stage closer to reality later this year. At least that is the rather optimistic hope of Imutran, a company researching the genetic manipulation of pigs in an effort to make their organs transplantable into humans. Imutran's spokesmen in England have said several times that the company expects to carry out the first human trial of its genetically modified xenografts in late 1996. The company's enthusiasm has not been widely shared, and various groups have been examining the desirability of developing animal-to-human transplants. The Nuffield Council on Bioethics reported[1] in March and the British Medical Association's ethics committee[2] in May. The government set up a committee as soon as it got wind of Imutran's intention to start human trials: the committee will report to ministers in July, but there is no indication of when its report will be published. The central problem with transplanting animal organs into humans is hyperacute rejection, which can destroy an organ's function within an hour. The interaction of natural antipig antibodies in the human with antigenic molecules in the donor organ initiates the with blood clotting and vasoconstriction. Imutran hopes to prevent the cascade by genetically engineering pigs to express specifically human regulators of complement activity. If it succeeds, however, it will only have overcome the hyperacute rejection. Other forms of rejection are still likely to happen; it is hoped that they can be suppressed by cyclosporin. One as vet unquantifiable risk is that microorganisms that are harmless to pigs but pathogenic in man may also be transplanted. The Nuffield Council addressed whether it is ever acceptable to use animals to provide donor organs and, if so, whether primates could be used. They concluded that the special protection afforded to primates ruled out their use, but approved the use of transgenic pigs, as long as they were subject to the same protections as other animals used in research. The council also took up questions concerning the timing of human trials, protection of patients' welfare, possible impacts on public willingness to donate human organs, as well as potential health risks to humans. The council recommended that several safeguards be put in place before human trials begin, including the establishment of a governmental advisory committee with the power to regulate xenografting, a code of practice, and standards and mechanisms for monitoring human recipients. …