Which organ transplant was performed first, in 1954, between identical twins?

The kidney, in Boston - Ronald Herrick gave one to his twin Richard, who lived another eight years. The twins were the point: identical genomes meant no rejection, so the surgeons could find out whether the operation itself worked before anyone knew how to suppress an immune system.

The team was accused of violating do no harm by cutting into a healthy man for someone else's benefit, and it took a court ruling and considerable soul-searching before they proceeded. Living donation is now routine and the ethical question has never entirely gone away.

The rest of transplantation waited on immunology. Early attempts between unrelated people failed within days until azathioprine and then ciclosporin - found in a soil fungus from Norway, developed in the 1970s - made it possible to hold rejection off without destroying the patient's defences entirely. The kidney remains the most transplanted organ, and the shortage is severe enough that pig kidneys with edited genomes reached human patients in 2024, with the recipients surviving weeks rather than years so far.