Baby Fae Surgeon to Continue Cross-Species Research
Dr. Leonard Bailey, the Loma Linda University surgeon who a year ago transplanted a baboon heart into Baby Fae, says he will continue to research the problems of cross-species transplantation and predicts that such daring, if controversial, operations may become commonplace for infants awaiting a new human heart.
Bailey, meeting with reporters this week, said he may perform another baboon-to-baby heart transplant as early as next year--if his current attempts to overcome some of the problems of cross-species transplantation bear fruit.
Despite criticism from many transplant immunologists, Bailey displayed calm assurance that he and his team are on the right track. But he said he would do it again only if he is convinced that the second baby would live longer than the 20-day survival of Baby Fae. The university’s Institutional Review Board would first have to give its approval.
Many medical scientists were critical of the Loma Linda team for implanting the baboon heart in Baby Fae without having done what they considered to be adequate laboratory studies to resolve the tendency of humans to reject an organ from another species. The criticisms were on both scientific and ethical grounds.
A long-awaited report that gives the most detailed immunological information yet published on Baby Fae--and the baboon who donated her heart--appears in today’s Journal of the American Medical Assn.
Baby Fae was born in Barstow on Oct. 14 with a heart disease called hypoplastic left heart syndrome, which is almost invariably fatal. She received the baboon heart at Loma Linda on Oct. 26 but later died, apparently as a result of massive blood clots caused by a mismatch between her blood type and that of the baboon.
In the journal, Bailey and the team’s immunologist, Dr. Sandra S. Nehlsen-Cannarella, present data to support their explanation of why the graft failed and why they believe that cross-species transplantation in infants is worth pursuing.
In an accompanying editorial, two transplant surgeons, Olga Jonasson of the University of Illinois and Mark A. Hardy of Columbia College of Physicians and Surgeons, agreed with the Loma Linda team that a heart from another species could serve as a suitable short-term “bridge” for babies until a human heart donor became available.
But the two surgeons rejected much of Bailey’s and Nehlsen-Cannarella’s immunological thinking about cross-species transplantation as “wishful thinking,” “improbable” or “incorrect.”
In a session with reporters, Bailey and Nehlsen-Cannarella responded to those criticisms by saying that Jonasson and Hardy used out-of-date research from the 1960s and 1970s on which to base their conclusions.
“The editorial was rather patronizing and reflected thought that is not current,” Bailey said. He also called the authors “inconsistent” for first implying that cross-species transplants may not be feasible and then saying that a baboon heart could serve as a bridge until a human transplant was obtained.
“If they would (only) forget about arguing and get on the bandwagon and discover that we are on to something important and we are going to pursue it,” Bailey said.
The scientific disagreement between the two groups appears to be based on different views of what can be done about the genetic differences in tissues that cause an organ to be rejected.
Traditionally, immunologists believe that organs from animals more distantly related to humans are more apt to be rejected by a human being than organs from animals more closely related to humans. Thus they believe that baboon hearts, for example, will trigger a much stronger rejection by the human immune system than chimpanzee hearts because baboons are more distantly related to man.
In contrast, Bailey and Nehlsen-Cannarella are working on the theory that there are major differences among individual animals within a species and that some of those individuals may be more compatible to certain human recipients than are other animals of a species that is actually more closely related to humans.
They also believe that it is possible to do tests on the prospective animal donors and on the human recipient that will predict which of the animal hearts is least apt to be rejected.
They said that, when selecting a donor, they focus their interest not on where the organ came from but on whether or not the tissues have strong similarities with the recipient’s.
But Jonasson and Hardy believe that it will not be possible to transplant organs from another species--especially one as distantly related as a baboon--until a way is developed to deactivate the proteins, or antigens, on the animal organ that trigger rejection by the human host’s immune system. In a telephone interview, Hardy added that one such way to prevent the rejection may be to expose the organ to ultraviolet light before implantation. Other researchers, he said, plan to use monoclonal antibodies, or so-called “guided-missile” antibodies, to deactivate the animal antigens.
The research currently being done by Bailey and Nehlsen-Cannarella involves a series of experiments in which an organ from one animal species is transplanted into another animal species. By varying the many donor and recipient factors that may be involved in producing rejection, they hope to learn which factors are optimal for producing the best results. They hope to complete these experiments by the end of next year.
Hardy, who is doing experimental animal cross-species studies at Columbia Presbyterian Hospital in New York, said he is “sorry” if his editorial gives the impression of disapproval of the Loma Linda work.
“We have all learned from Bailey’s experience that xenografts (organs from another species) have not reached the point where it can be hoped they can replace a human heart permanently,” Hardy said. “Our attitude at this time is that xenograft hearts are feasible and that they may be used as a bridge that is more efficient and cost-effective than the mechanical heart.”
