Immune system may trigger a form of heart disease

January 12, 2001

By Amy Norton

NEW YORK, Jan 11 (Reuters Health) - The chronic heart muscle disorder known as

dilated cardiomyopathy is thought to be brought on by a variety of factors--from

heredity to chronic, heavy drinking. Now, new research in mice suggests that in

some cases, the body's own immune system may be behind the life-threatening

condition.

Dilated cardiomyopathy is marked by diseased heart muscle fibers that result in

abnormal enlargement of one or more of the heart's chambers. This weakens the

heart's ability to pump efficiently and can trigger heart failure. Although in

some cases clear genetic or environmental causes can be determined, in other

cases the cause may remain unknown.

But one explanation may rest in the body's immune system, according to study

findings published in the January 12th issue of Science. Japanese researchers

report that in some cases, a misguided immune system assault may inflict the

damage seen in dilated cardiomyopathy.

Dr. Tasuku Honjo of Kyoto University in Japan led the study. Honjo told Reuters

Health that researchers have speculated the disease may involve an abnormal

immune response because some patients have been shown to have antibodies to

their own muscle protein and to certain chemical receptors.

However, Honjo noted, it has been unclear whether these so-called

" autoantibodies " are the cause or a result of dilated cardiomyopathy.

In the current study, the investigators found that a strain of mice lacking an

immune system regulator known as PD-1 developed a form of dilated

cardiomyopathy. All of the affected mice showed autoantibodies to a protein on

the surface of heart muscle cells.

Honjo's team also found that a second strain of mice without PD-1 did not

develop the heart disease. This, they report, suggests that other genetic

factors are also involved.

If these findings are confirmed in humans, it may be possible to treat some

cases of dilated cardiomyopathy with drugs that suppress the immune system or

possibly with gene therapy, Honjo said.

SOURCE: Science 2001;291:319-322.

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