More MS news articles for November 1999

Michael Woods: Environment may damage immunity

November 29, 1999

Is something in the environment messing up the immune systems of millions of people in the United States - in ways that put women at special risk?

What are these "environmental immunotoxins,'' or immune system poisons? Are they in the air, water, food, or drug supply? How do they work?

The final report of a National Institutes of Health (NIH) conference on environmental causes of autoimmune diseases, issued in October, gives a clear answer to the first question: Scientists are convinced that environmental factors can trigger autoimmune diseases.

A person, for instance, may be conceived with the genetic vulnerability to a disease. He or she may inherit a gene that predisposes him or her to the disease. The disease actually occurs, however, only if the individual comes into contact with Agent X in the environment.

Agent X may be a virus or bacteria, a prescription or non-prescription drug, an air or water pollutant, a chemical used in industrial or commercial products, a food, or some other material.

At least 10 million Americans have an autoimmune disease, which occurs when the body's immunological defense system goes haywire. The immune system normally protects the body from illness. It attacks bacteria, viruses, abnormal cells, and other material that doesn't belong.

In autoimmune disease, the immune system attacks normal body cells and causes illness. In insulin-dependent diabetes, for instance, the immune system attacks insulin-producing cells in the pancreas. In multiple sclerosis, it attacks nerve cells. In autoimmune thyroiditis, it attacks the thyroid gland. In rheumatoid arthritis, it attacks the joints. In lupus, the immune system may destroy cells in the heart, kidney, and other organs.

Those conditions are among more than 80 different disorders in the family of autoimmune disease. Some, like autoimmune thyroiditis, are mysteriously increasing in frequency.

At least two incidents that experts describe as "epidemics'' of environmentally-induced autoimmune disease have occurred. In Spain in 1981, 35,000 people developed immune disorders after eating contaminated cooking oil. In the late 1980s, at least 1,500 Americans became ill from consuming contaminated batches of L-tryptophan, a dietary supplement.

NIH's National Institute of Environmental Health Sciences in Research Triangle Park, N.C., sponsored the conference. It brought together more than 100 authorities, who reported on the latest discoveries about environmental causes of autoimmune diseases.

Some of the best evidence for Agent X has emerged from studies of identical twins, researchers reported. Identical twins inherit virtually the same genes, and genetic vulnerabilities to disease. Yet autoimmune disease often occurs in just one twin - perhaps the individual who came into contact with an environmental immunotoxin. Identical twins both get the same autoimmune disease only 25 to 40 per cent of the time.

For unknown reasons, 75 per cent of autoimmune disease cases occur in women. Scientists suspect that the female sex hormone, estrogen, may make women especially susceptible to some environmental immunotoxins.

New evidence suggests that prenatal exposure to environmental immunotoxins may be more dangerous than exposure during adult life. Animal studies show that prenatal exposure to certain pesticides and industrial chemicals results in permanent immune system damage.

The report also described evidence that "a large number'' of drugs and environmental chemicals make people produce immune system proteins that can attack body cells. Scientists don't know whether these proteins, or "autoantibodies,'' pose an actual threat of disease.

Autoimmune problems may be far more common than estimates suggest. They may be a factor the fatigue, headaches, muscle and joint pain, and other minor routine health complaints that diminish the quality of life for millions.