The Associated Press

Blood from umbilical cords can build new immune systems for adults with leukemia, offering a potentially lifesaving treatment for the many patients who cannot find suitable bone marrow donors.

Currently, an estimated 4,000 to 6,000 Americans die each year while awaiting a bone marrow match.

Until now, stem cells drawn from umbilical cord blood have been reserved mostly for treating children. Because an umbilical cord contains only one-tenth as many stem cells as a marrow donation, experts believed there was too little tissue to reconstitute the immune defenses of an adult.

However, new research shows that because the umbilical cord cells proliferate so rapidly, they can indeed be used to treat adults.

In the first U.S. study of cord blood transplants in adults, researchers at University Hospitals of Cleveland and other sites gave 68 adults cord blood transplants from unrelated donors.

While infections, bleeding and other complications killed many of the patients within months, nearly one-third survived long term, about the same as with bone marrow transplants.

``This field will explode'' and may even replace bone marrow and other sources of stem cells, said Dr. Andrew L. Pecora, director of the blood and marrow stem cell center at Hackensack University Medical Center in New Jersey. ``Cord blood transplantation holds the promise of making it so everyone has a donor.''

The research is reported in Thursday's New England Journal of Medicine.

Stem cells, collected from bone marrow or circulating blood in adults or from cord blood, are immature cells that can develop into any type of blood cell: oxygen-carrying red blood cells, clotting platelets or infection-fighting white blood cells.

In patients with leukemia and other blood disorders, doctors destroy the cancer and the immune system with chemotherapy or radiation, then replace the patient's immune- and blood-forming system with a transplanted one.

Cord blood stem cells are collected by hospitals before placentas are discarded and so do not involve the controversy over use of stem cells from fetuses. Cord blood cells, stored frozen at public stem cell banks, offer other key advantages.

They are immunologically ``naive,'' unlike cells from adults, and are thus far less likely to trigger a common, life-threatening complication called graft-versus-host disease, in which the transplanted immune system attacks the patient's tissue. In this study, only 18 percent of patients developed the complication, about the rate in patients getting marrow from a matched sibling.

That gives doctors far more leeway in finding a matching stem-cell donor. Currently, only about 60 percent of white Americans now find a suitable donor, and the rates for minorities range from just 20 percent to 50 percent.

In addition, Dr. Mary J. Laughlin, director of the transplant program at University Hospitals of Cleveland, noted that a cord blood stem cell match can be located and prepared within weeks, rather than the months it takes to arrange a bone marrow transplant.

And cells from newborns are unlikely to contain a virus dangerous to transplant patients that lurks harmlessly in most adults.

Laughlin expects that within five years, stem cells from cord blood will be used for repairing damaged blood vessels in heart and stroke patients, repairing brain tissue in Parkinson's disease patients and, in diabetics, replacing pancreas cells that are not producing enough insulin.

Meanwhile, because cord blood cell recipients fare better the more cells they receive, Pecora and other researchers are developing ways to make stem cells from cord blood multiply in the lab so there are more cells to transplant.

Liana Harvath, director of the blood resources program at the National Heart, Lung and Blood Institute, said researchers also must find a way to cut the time it takes for cord blood stem cells to build new immune- and blood-forming systems.

In an editorial, Dr. Eliane Gluckman of Hopital Saint-Louis in Paris called the results remarkable but recommended that doctors still search both bone marrow and cord-blood registries to find the best available match.

Copyright 2001 The Associated Press. All rights reserved.