Organ transplant patients face a catch-22. The powerful drugs that suppress their immune systems and protect their new organs from rejection can cause life-threatening side effects, including high blood pressure, susceptibility to infection and even cancer. Now researchers at the University of Pittsburgh Medical Center have found a link between a patient's genes and the chances of rejection that could free many patients from lifelong dependence on immunosuppressant drugs.

Physicians have long known that certain people are more prone to deadly rejection episodes than others, regardless of how well a donor organ is "matched" to their bodies. Studying children who received new hearts, a team led by immunologist Adriana Zeevi has now shown that immune molecules called cytokines are a likely culprit. Cytokines kick the immune system into high gear, revving it up to eliminate foreign invaders -helpful if the intruder is a virus, bad if it's a desperately needed kidney or liver. Zeevi showed that patients whose bodies produce more of a cytokine called TNF-alpha, but less of the cytokine IL-10, were most likely to reject their new organs.