Reducing immunosuppression to fight infection triggers rejection

Xenotransplant recipients require far more aggressive immunosuppression than human-to-human transplant recipients, but the immunosuppression itself leaves them vulnerable to infections. When an infection occurs, clinicians must reduce immunosuppression to let the patient's immune system fight the pathogen, but reducing immunosuppression allows the patient's immune system to simultaneously attack the pig organ. This is exactly what happened to Towana Looney in 2025: she received a pig kidney at NYU Langone in November 2024 and lived with normal kidney function for over 4 months, but when she developed an unrelated infection, her immunosuppression was lowered, and her immune system rejected the pig kidney. The organ was surgically removed after 4 months and 9 days. This is a structural catch-22 with no current solution: the level of immunosuppression needed to protect a xenograft is incompatible with the level of immune function needed to survive routine infections. In human-to-human transplants, the margin is wider because the immune response to allografts is weaker. In xenotransplants, the margin is essentially zero.