The natural antibodies (blood proteins) most people have would destroy an organ from someone of a different blood type, so transplant patients historically had to have a compatible blood type donor. But by filtering the blood of antibodies and giving patients a medication that prevents the antibodies from coming back, doctors are crossing these barriers. The combined treatment has been successful both for patients who are considered "ABO incompatible," meaning their blood type – A, B, AB or O – differs from their donor, and for those who are "sensitized" to proteins in their donor's tissues from exposure to these factors during previous transplants, blood transfusions or pregnancies.
Data to be presented April 30 at the American Transplant Congress meeting in Washington show that 27 of 29 kidney patients transplanted at Hopkins after participating in the program are doing well, with no sign of organ rejection. Like all transplant patients, they take daily medications after transplant to suppress rejection. One kidney failed after transplant because the patient stopped taking these medications.
"Many of these patients have repeatedly been told there is no hope of ever receiving a kidney transplant," says Robert A. Montgomery, M.D., D.Phil., lead author of the study and assistant professor of surgery. "With this innovation, I can tell any patient who has a live donor and is medically eligible that they can be transplanted with a high likelihood of success. This procedure has the potential of increasing the number of living donor transplant operations by one-third to one-half."
A live donor operation – where the transplant patient receives a kidney from a live person (most commonly a friend or relative) – is far preferable to transplanting an organ from a cadaver, Montgomery says. On average, the kidneys last twice as long, they work right away, total hospital costs are reduced and patients have a shorter hospital stay. Nearly 52,000 people are on the national waiting list for a kidney, according to the United Network for Organ Sharing.
In their technique, Montgomery and colleagues gave the transplant recipients an average of three or four plasmapheresis treatments every other day starting a week to 10 days before surgery, and three additional treatments the week after. During plasmapheresis, the fluid part of the blood, called plasma, is removed from blood cells by a device known as a cell separator. The separator works by spinning the blood at high speed to separate the cells from the fluid. The cells are returned to the person undergoing treatment, while the plasma, which contains the antibodies, is discarded and replaced with other fluids. Doctors also gave patients an intravenous drip of a medication designed to prevent the antibodies from returning and to make patients less likely to get an infection.
Montgomery and colleagues looked at 29 patients enrolling in the program since its inception in 1998. Five patients had incompatible blood types with their donors, and 24 had incompatible tissue proteins. Today, an average of 17 months after surgery, 27 of the transplanted kidneys are functioning well, with normal levels of creatinine, a simple measure of kidney function.
Other initiatives at Hopkins to allow more kidney transplants from live donors include an altruistic donor program, where anyone who comes forward to offer a kidney will be matched to a recipient, and a paired kidney transplant program. In the paired kidney program, or donor swap, two donor-recipient pairs with incompatible blood types are matched so the donor from one pair gives a kidney to a recipient of another pair, and vice versa. In the match-up, the donors and recipients have compatible blood types and require no special therapy before the transplant.
Other study authors were Milagros D. Samaniego, M.D.; Andrea A. Zachary, Ph.D.; Christopher J. Sonnenday, M.D.; Daniel S. Warren, Ph.D.; Ernesto P. Molmenti, M.D.; and Lloyd E. Ratner, M.D.
Abstract #94164547: Montgomery, R. et al, "Differing Patterns of Antibody Suppression and Re-emergence between ABO Incompatible and Positive Crossmatch Kidney Transplants."
Related Web sites:
Johns Hopkins' Comprehensive Transplant Center
http://www.hopkinsmedicine.org/transplant
American Transplant Congress - annual meeting
http://www.atcmeeting.org
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