• A baby born with a thymic deficiency received what many consider the world’s first heart transplant combined with a thymus implant.
• Six months on, the recipient is reportedly thriving.
• With the donor thymus, the recipient can make T cells that recognize the donated heart as its own, reducing the chance of rejection.
• This procedure could allow doctors to carry out transplants without relying on lifelong immunosuppressant medication against organ rejection.

Doctors at Duke University Hospital in North Carolina have, in a pioneering procedure, successfully transplanted a heart combined with a processed allogeneic thymus tissue. The recipient — a baby who was 6 months old at the time — has just celebrated his first birthday.

The infant seems to be now producing the immune cells necessary to reduce or even eliminate the need for long-term treatment with antirejection drugs.

‘Pioneering’ research

Scientists at Duke have been studying the potential of transplanted thymus cells for some years. A thymus transplant is a relatively new treatment for infants born without a functioning thymus, a possible characteristic of complete DiGeorge anomaly, a rare congenital condition. The thymus gland sits within the chest between the lungs and behind the breastbone, and it is an important part of the body’s immune system.

Infants without a functioning thymus cannot manufacture T cells. This leads to severe immunodeficiency, so they cannot fight off infections and typically die by the age of 3 years.

Scientists at Duke have published two previous studies of thymus transplants in infants with complete DiGeorge anomaly. In their studies, more than 70% of the infants survived for at least 2 years after the transplant.

Before the transplant, the donor thymus undergoes several processes, which a team, led by Dr. Mary L. Markert, M.D., at Duke, developed. In 2012, Dr. Markert began animal studies to investigate the use of cultured thymus tissue implants (CTTI) in organ transplants.

The procedure

In this case, the recipient — 6-month-old Easton Sinnamon — was born with severe heart abnormalities and thymic deficiency from an unknown cause. He needed both a heart transplant and an implant of processed thymus tissue, independent of each other. The researchers received permission from the Food and Drug Administration (FDA) to carry out both procedures together.

Surgeons carried out the heart transplant when Easton was 6 months old. They implanted cultured thymus tissue from his heart donor 2 weeks later.

By using both the heart and the thymus tissue from the same donor, doctors hoped the baby’s body would be less likely to reject the organs.

When doctors performed tests 172 days after the implantation, they found that the processed thymus tissue was functioning and producing T cells. They will continue to monitor Easton’s progress and hope to reduce his antirejection drugs over the coming months.

The future of organ transplants

Following organ transplants, patients usually have to take antirejection medications and other medications for the rest of their lives. These drugs, which suppress the immune system, have side effects that can be highly toxic or make it hard to fight off infections. They may also increase the risk of diabetes and cancer.

Apart from reducing the chances of organ rejection, doctors hope this procedure could also eliminate the need for recipients to take these lifelong immunosuppressant treatments.

“This case has implications for more than just heart transplantation — it could change the way that many solid organ transplants are done in the future.”

– Dr. Allan D. Kirk, M.D., Ph.D., chair of the Department of Surgery at Duke University School of Medicine.

The scientists at Duke are interested in investigating whether healthcare professionals could use the thymus transplant technique in patients with a functioning thymus. The use of CTTI may help restructure the recipient’s immune system, so they do not have to rely on antirejection medication.

A 2011 study stated: “In the last quarter-century, much has been learned about infant heart transplantation. But, much remains to be discovered.”

Perhaps the findings in this latest case will be one of those discoveries that moves not only infant transplants but also adult transplants forwards.

Many experts are optimistic:

“This has the potential to change the face of solid organ transplantation in the future.”

– Dr. Joseph W. Turek, M.D., Ph.D., Duke’s chief of pediatric cardiac surgery and a member of the surgical team.

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