Mix, Match, and Switch
Kidney exchanges between strangers are helping to ease the organ shortage and could save thousands of lives
The evidence has become so compelling that at the end of August, UNOS proposed a plan for a national swap system. There is, however, a small hurdle. Kidney exchanges may violate a federal law against selling body parts. "We're very excited about exchanges," says Bill Lawrence, director of patient affairs at UNOS, "but we can't move ahead until Congress clarifies the law." And Congress, consumed by the run-up to the November elections, hasn't leapt at the chance to bring clarity yet. In the meantime, hospitals have begun to band together to create larger pools of pairs on their own.
The biggest nonlegal barrier standing between patients and a new kidney, and the one that kidney swaps aim to surmount, is biological: the immune system. That intricate defense network comes armed with antibodies-molecules that mark other cells for destruction-and after identifying a body part as a foreign object, the system tries to kick it out.
One reason that body parts appear strange to the immune system is blood type. There are four types: A, B, AB, and O. If they don't match between donor and recipient, the organ may be rejected. Body parts also need to be in sync on tissue type. "There are six common 'flavors' of tissue," says Robert Montgomery, chief of the transplant center at Hopkins. "And if you have antibodies against one of those flavors, it's very hard to find someone who will match you." More than one type of antibody, or just high levels of one type, make a match almost impossible. It's called being highly sensitized. People develop sensitivities against other tissue types because they are exposed to them. Mothers, for example, get exposed through pregnancy-the fetus carries genes from the father, after all-and anyone can get exposed through blood transfusions.
Most hospitals do not have enough expertise with sensitivity to try to work around it. So these cruel immunological twists are why many loved ones, willing to sacrifice almost anything to save the life of a father, a sister, a wife, or a best friend, remain sidelined, unable to donate a needed organ. Paired donors are a way around this. "Instead of having just one recipient and one mismatched donor, we can put them into a whole pool of donors and find them a better match," Montgomery says. These are not perfect matches, he adds, but the level of antibodies is low enough that they can be controlled by immunosuppressive drugs and a treatment called plasmaphoresis that filters antibodies out of the blood.
Separation. It's a little after 8 a.m. Montgomery is in his scrubs, preparing to enter Adamson's operating room. Down the hall, another surgical team is already working on Williams. And in an adjacent hospital building, two more teams are starting surgery on the Balhatchets. "We keep the pairs completely separate and anonymous," says Kathy Dane, one of the hospital's transplant coordinators. "We really don't want them getting entwined in each other's lives before the surgery, because that could lead to pressure on someone to go through with surgery even if they have some doubts."
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