Scientists are hoping to train the body to accept new organs

Monday, February 11th, 2019

Before the discovery of anti-rejection drugs, organ transplants were simply impossible, but anti-rejection drugs are immune-depressant drugs. Now scientists are hoping to train the body to accept new organs:

In 1953, Dr. Peter Medawar and his colleagues in Britain did an experiment with a result so stunning that he shared a Nobel Prize for it. He showed that it was possible to “train” the immune systems of mice so that they would not reject tissue transplanted from other mice.

His method was not exactly practical. It involved injecting newborn or fetal mice with white blood cells from unrelated mice. When the mice were adults, researchers placed skin grafts from the unrelated mice onto the backs of those that had received the blood cells.

The mice accepted the grafts as if they were their own skin, suggesting that the immune system can be modified. The study led to a scientific quest to find a way to train the immune systems of adults who needed new organs.

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Many types of white blood cells work together to create and control immune responses. A number of researchers, including Dr. Markmann and his colleague, Dr. Eva Guinan of the Dana-Farber Cancer Institute, chose to focus on cells called regulatory T lymphocytes.

These are rare white blood cells that help the body identify its own cells as not foreign. If these regulatory cells are missing or impaired, people can develop diseases in which the body’s immune system attacks its own tissues and organs.

The idea is to isolate regulatory T cells from a patient about to have a liver or kidney transplant. Then scientists attempt to grow them in the lab along with cells from the donor.

Then the T cells are infused back to the patient. The process, scientists hope, will teach the immune system to accept the donated organ as part of the patient’s body.

“The new T cells signal the rest of the immune system to leave the organ alone,” said Angus Thomson, director of transplant immunology at the University of Pittsburgh Medical Center.

Dr. Markmann, working with liver transplant patients, and Dr. Leventhal, working with kidney transplant patients, are starting studies using regulatory T cells.

At Pittsburgh, the plan is to modify a different immune system cell, called regulatory dendritic cells. Like regulatory T cells, they are rare and enable the rest of the immune system to distinguish self from non-self.

One advantage of regulatory dendritic cells is that researchers do not have to isolate them and grow them in sufficient quantities. Instead, scientists can prod a more abundant type of cell — immature white blood cells — to turn into dendritic cells in petri dishes.

“It takes one week to generate dendritic cells,” Dr. Thomson said. In contrast, it can take weeks to grow enough regulatory T cells.

The regulatory T cells also have to remain in the bloodstream to control the immune response, while dendritic cells need not stay around long — they control the immune system during a brief journey through the circulation.

“Each of us is taking advantage of a different approach,” Dr. Markmann said. “It is not clear yet which is best. But the field is at a fascinating point.”

Comments

  1. Kirk says:

    The mere existence of chimeras points to there being an already-existent mechanism for dealing with immune problems stemming from transplants. Why nobody is really looking at that is something I’d dearly love to know…

  2. Sam J. says:

    It’s got to be real soon now that they start using genetic engineering on pigs to build hearts, lungs, and livers for humans.

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