Xenotransplantation and Transgenics: The Need to Discuss Limits

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.

Transplantation of human organs and tissues is now a commonplace in the world of high technology medicine and powerful immunosuppressants. Nevertheless, there are still far too few organs available to those who need them. At any given time there are 30,000 to 60,000 people waiting for transplantable organs. This phenomenon has led to an amazing array of suggested solutions to the problem, such as presumed consent, artificial organs, non-heart beating cadaver protocols, and offering economic incentives to the families of organ donors. None of these have met with widespread acceptance.

Another potential solution to this dilemma is xenotransplantation, a procedure that promises to be high on the list of topics at this year's international conference, TRANSPLANT 2000, to be held in Chicago the week of May 14-20.

Xenotransplantation, from the Greek word "xenos," which means "foreign" or "strange," is the transplantation of an organ or tissues from one species to another. In most cases, of course, discussions about xenotransplantation are about transplanting animal organs into human beings, not vice versa.

There are, obviously, huge technical hurdles to be cleared before xenotransplantation could proceed on any kind of widespread basis. Other significant barriers include the antipathy of the public toward certain forms of xenotransplantation. For instance, while there is some squeamishness among the general public about using pig hearts or livers for transplant, there is significantly greater disapprobation toward killing higher order primates, like baboons, for their organs. Whether there is an important moral difference in killing a pig versus a baboon is an interesting question worth pursuing, but not here.

Should we xenotransplant? Should we transfer the organs of a non-human species to Homo sapiens? My own answer is a qualified yes. That is to say, I can find no ethical reason why, all things being equal, we should not invest in xenotransplantation research. If one thinks that traditional transplantation can be ethical, given appropriate ethical considerations (like informed consent, for instance), on what basis would it be wrong to use organs from animals?

The problem is my qualification: "all things being equal." We all know that seldom are all things equal. While I do not find xenotransplantation ethically problematic per se, there are manifold worries that ought to give us pause as we develop this technology.

In their recent volume Xeno: The Promise of Transplanting Animal Organs into Humans (Oxford, 2000), David Cooper and Robert Lanza cover some of the difficult ethical issues surrounding the procedure. The greatest concern has arisen over the possibility of a virus mutating across species and creating a plague-like epidemic which would take some time and many lives to control. This is a real concern, and we should err on the side of caution.

Informed consent and patient confidentiality are paramount issues in xenotransplantation. Patients should know exactly what they are getting into (or what's getting into them), and they alone should determine who knows that they have porcine islet cells or a baboon heart. Even more difficult questions arise when we combine xenotransplantation with transgenics. Transgenics is the science of mixing animal and human genes. This is an area of tremendous potential since genetically altering tissues from a pig by adding human genes, for instance, could result in far less immunoresistance or, ideally, none.

That would mean, of course, that the expensive and potentially dangerous side effects of immunosuppresant drugs would be alleviated altogether. Transgenics, however, lead down a path that is likely to be very thorny. Just what percentage of human genes make an animal more than animal, and what percentage of animal genes make a human less than human? It's a question that may seem far-fetched, but we have to remind ourselves constantly these days that what used to be science fiction is now science fact.

The United Kingdom's Advisory Group on the Ethics of Xenotransplantation has opined that "some degree of genetic modification is ethically acceptable" but that "there are limits to the extent to which an animal should be genetically modified" (Xeno, p. 195).

But just what are those limits? And who sets them? And on what basis? These are issues right at the contemporary crux of ethics and medicine, yet no one (or at least precious few) seems to be talking about them. We are not likely to garner a great deal of ethical insight from TRANSPLANT 2000. That's not a pejorative comment, that's an historical fact. Most of those conferences focus on what we can do, not what we should do. The prescriptive must govern the descriptive but, sadly, we usually do it the other way around.

Editor's note: For background on this commentary, see the press release "Organ Shortages, Stem-Cell Discoveries, and Xenotransplantation to Be Highlighted at International Transplantation Meeting" located at prnewswire.com.

C. Ben Mitchell, PhD, is a senior fellow of the Center for Bioethics and Human Dignity and teaches Bioethics and Contemporary Culture at Trinity International University's Trinity Evangelical Divinity School. He also serves as bioethics consultant for the Ethics and Religious Liberty Commission of the Southern Baptist Convention.