Postmortem in Baby Fae.

The newborn baby who died three weeks after receiving a baboon heart in October 1984 succumbed to a "potentially avoidable" immune response, her medical team now reports.

Although the baby died because the transplanted heart tissue died, "hyperacute rejection did not occur," Leonard L. Bailey and his colleagues at California's Loma Linda University report in the Dec. 20 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION. A cross-species transplant might have worked with closer tissue matching and other changes in procedure, they say.

White blood cell recognition and attack of foreign tissue is the primary problem in human-to-human heart transplants. But in the baboon transplant, the rejection was orchestrated primarily by antibodies, the researchers report. Though they used cyclosporine, the immune suppressant is thought to work best against the white cell response.

The infant, known as Baby Fae, was born with hypoplastic left heart syndrome, a congenital heart malformation that kills most babies within a month of birth. Other options for Baby Fae were a difficult and often unsuccessful two-step surgical procedure or a human heart transplant. the researchers say that while a human heart transplant is the most desirable option, it is "impractical" in infants. Nevertheless, last month Bailey transplanted a human heart to a 4-day-old boys. At press time the boy was off life-support systems and healthy, according to a university spokesperson.

Baby Fae's transplant was not only cross-species, it was cross-blood-type. Baby Fae was type O, which is rare in baboons. Bailey used a heart from a AB baboon selected because of other typing matches and minimal reaction between the baboon's blood and the baby's in culture.

Kidneys, livers and hearts from chimps and baboons have been implanted in humans before, but with little success. The Loma Linda operation (SN: 11/3/84, p. 276; 11/24/84, p. 325) was the first cross-species heart transplant done since the advent of cyclosporine.

The supposition made by the Loma Linda team that a relatively immature immune system would mount less of a rejection response was "wishful thinking," Olga Jonasson of the University of Illinois in Chicago and Mark A. Hardy of Columbia University in New York City claim in an accompanying editorial. But, they say, Bailey has demonstrated that a cross-species heart transplant is technically feasible, and that such a transplant might provide a "bridge" until a human heart is available.