INJECTIONS PREVENT REJECTION OF ORGANS AFTER TRANSPLANTS

                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: FRIDAY, February 28, 1992                   TAG: 9202280193
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A-5   EDITION: METRO 
SOURCE: Associated Press
DATELINE: WASHINGTON                                LENGTH: Medium
INJECTIONS PREVENT REJECTION OF ORGANS AFTER TRANSPLANTS
Hearts transplanted between incompatible lab mice can be protected from rejection by a technique that creates a molecular shield against attack from the immune system, a new study shows.
In a work to be published today in the journal Science, researchers report that they used two types of laboratory antibodies to prevent the host immune system from recognizing that the transplanted hearts were foreign tissue.
Dr. Mitsuaki Isobe, now with the University of Tokyo, said his research team used two types of laboratory mice that had significantly different immune systems. This means that tissue transplanted from one mouse strain to the other normally would be rejected, just as an immune system would attack and reject an invading bacteria.
In some of the mice, hearts were transplanted between the strains with no attempt to prevent rejection.
In others, the receiving mice were injected for six days with what are called monoclonal antibodies. These are laboratory-made antibodies that block the action of specific molecules in the host. In this case, the antibodies were designed to block the action of molecules on the surface of T-lymphocytes, a type of blood cell that normally attacks the foreign tissue.
Isobe reported that in mice that did not receive the injections, the transplanted hearts quickly stopped.
In mice treated with the monoclonal antibodies, the transplanted hearts continued to live and function for up to 200 days, the limit of the experiment. Microscopic studies of the transplanted organs detected no signs of active rejection.
As a further test, Isobe said, mice receiving the antibody shots later were given skin grafts from a third strain of mice. These skin grafts were rejected.
Isobe said the skin test proved that the immune system of the mice continued to protect them from infection and other foreign tissue.
In most human organ transplants, patients must undergo lifelong treatment with immune-suppression drugs.
"These drugs suppress all immunity," said Isobe. But "these antibodies are antigen-specific." This means that the immune system is tricked into ignoring only the transplanted organ and remains active against germs.
By using specific antibodies, he said, patients may not need lifelong drug treatment to avoid organ rejection.

by Bhavesh Jinadra by CNB