Magazine article Science News

Cholera Toxin Fights Autoimmune Disease

Magazine article Science News

Cholera Toxin Fights Autoimmune Disease

Article excerpt

The many cells and chemicals that make up the body's elaborate immune system are supposed to hunt down and vanquish invaders -- largely bacteria, viruses, and foreign tissues that threaten health. But for reasons no one quite understands, immune system components sometimes get confused and begin attacking familiar, benign elements of the body.

Researchers in Sweden have begun harnessing a fragment of the cholera toxin in a novel approach to thwarting autoimmune disease -- the general term for immune attacks against the body's own tissue. The new therapy, described in Atlanta last week at the annual meeting of the American Association of Immunologists, held as part of Experimental Biology '95, promotes tolerance of a substance that the immune system had previously recognized as foreign by attaching it to a cholera toxin fragment.

When fed to animals, a single, small dose of this combo permanently shut down either of two experimentally induced autoimmune diseases, reported study leader Cecil Czerkinsky of the University of Goteborg in Sweden.

Of the two primary components of cholera toxin, only the A chain is actually poisonous. The B chain not only anchors the molecule to the intestine, it also stimulates the immune system. Drawing on the idea that individuals can sometimes develop a tolerance to antigens -- substances that cause an immune reaction -- by eating them, Czerkinsky's team fed its animals sample antigens linked to B chains.

In the intestines, the strategy "induced a very strong antibody response to the [antigen]," Czerkinsky notes. "But at the same time, these animals developed a profound state of tolerance in the periphery -- the blood and lymph nodes." And that led his group to investigate the B chain for blunting undesirable immune responses in animals.

They began by "gluing" the B chain to myelin basic protein, a material that sheathes nerves and falls under immune attack in multiple sclerosis (MS). …

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