In 1984, a premature infant who urgently needed a heart transplant drew national attention when doctors implanted a baboon’s heart to replace her failing one. The unconventional surgery quickly became a widely discussed event, not only for its medical ambition but also for the debate it ignited among medical ethicists and animal rights advocates. While supporters saw it as an attempt to save a life during a time of limited alternatives, critics questioned the ethical implications of using animal organs and performing such an experimental procedure on a newborn.
In October 1984, a surgical team at Loma Linda University Medical Center in California carried out a procedure that drew global attention. Surgeons performed the first baboon-to-human heart transplantation into a one-month-old infant, later known to the public as “Baby Fae.” The team attempted the operation because the infant had a fatal congenital heart defect and no human donor heart was available at the time.[1] The procedure drew criticism as soon as it became public. Both animal rights groups and medical ethicists questioned the decision.
Baby Fae was born with hypoplastic left heart syndrome (HLHS), a condition in which the left side of the heart is too small to pump blood effectively. In the early 1980s, treatment options for HLHS were extremely limited, and infant heart transplantation had not yet become standard practice.[1]
Dr. Leonard L. Bailey, a pediatric cardiac surgeon, led the team that transplanted a baboon heart into Baby Fae on 26 October 1984. The goal was to keep her alive long enough for a human donor heart to become available. The team turned to a baboon donor because infant human hearts were scarce and xenotransplantation was being explored as a temporary solution.[1]
The operation was performed at Loma Linda University Medical Center in California, and Baby Fae lived with the xenograft for 21 days, until she died on 15 November 1984.
At that time, organ shortages created a major barrier in pediatric heart transplantation. Xenotransplantation—transplanting organs from one species into another—was viewed as a potential short-term strategy to address the gap until more reliable human-to-human infant transplantation could be established.[1] The field was still emerging, and the physiological similarity between primates and humans made such attempts scientifically relevant.
Surgeons used cardiopulmonary bypass to support Baby Fae’s circulation during the procedure. After removing her failing heart, they implanted the baboon heart, which began functioning immediately. To prevent rejection, Baby Fae received cyclosporine, an immunosuppressant that had recently transformed transplant medicine.[1]
However, a major challenge emerged: the baboon donor had a different blood type, and incompatibility likely contributed to the eventual rejection of the organ. Despite early signs of improvement—including stable heart function and improved breathing—she developed progressive rejection and multi-organ failure by the third week of life.[1]
Controlling immune rejection remains a central challenge. Both early (innate) and later (adaptive) immune pathways can damage the graft. Investigators are studying indicators such as CD3, CD4, CD8, as well as cell-free DNA and certain microRNAs, to detect rejection at an early stage.
Modern xenotransplantation relies on pigs that carry multiple gene edits. These edits remove immune-triggering surface sugars and introduce human genes to make the organ more compatible with human physiology.
Alongside conventional drugs, newer methods are being explored. These include costimulation-blocking therapies to dampen T-cell responses and approaches that target innate immune cells or specific antibodies.
Organ-support technologies such as machine perfusion are being developed to reduce injury during storage and improve the condition of the organ before transplantation.
Researchers emphasize strict viral screening of donor pigs, particularly for PERVs (porcine endogenous retroviruses), and close monitoring of recipients to reduce infection risks.
Current discussions focus on clear criteria for patient selection, standardized risk evaluation, and transparent regulatory processes, with attention to both human safety and animal welfare.
Although the transplant did not succeed long-term, the case demonstrated that a non-human primate heart could function in a human infant for days to weeks under immunosuppression. The procedure stimulated research into immune rejection, donor-recipient matching, and ethical guidelines for experimental surgery. Within a year, the first successful infant-to-infant heart transplant was completed, partly driven by insights from Baby Fae’s case.[3]
References
1. Bailey LL, Nehlsen-Cannarella SL, Concepcion W, Jolley WB. Baboon-to-human cardiac xenotransplantation in a neonate. JAMA. 1985 Dec 20;254(23):3321-9. PMID: 2933538.
2. Arabi TZ, Sabbah BN, Lerman A, Zhu XY, Lerman LO. Xenotransplantation: Current Challenges and Emerging Solutions. Cell Transplant. 2023 Jan-Dec;32:9636897221148771. doi: 10.1177/09636897221148771. PMID: 36644844; PMCID: PMC9846288.
3. Ekser B, Li P, Cooper DKC. Xenotransplantation: past, present, and future. Curr Opin Organ Transplant. 2017 Dec;22(6):513-521. doi: 10.1097/MOT.0000000000000463. PMID: 28901971; PMCID: PMC5935127.
Edited by M Subha Maheswari
