Stump the Scientist Scenes from AAAS Science After Hours


February 18, 2001

Autoimmune Disease: Why Women?
Two explanations for why women get autoimmune diseases more often than men
by Pearl Tesler

Autoimmune diseases are ones in which the body attacks itself. The immune system, which ordinarily targets foreign cells, starts attacking cells of the body.

Women are especially susceptible to autoimmune diseases, which include rheumatoid arthritis, thyroid diseases, lupus, multiple sclerosis, and Type 1 diabetes. In fact, of the ten million plus people in the United States suffering from autoimmune diseases, 75% are women. How come?

Researchers at AAAS presented two possible explanations today.

Sara Walker, rheumatologist at the University of Missouri, explained that the male hormone testosterone may play a protective role, by (somehow) suppressing autoimmunity. In studies of mice with lupus, injections of testosterone caused remission and longer life. When mice with lupus were injected with the female hormone estrogen, deaths from the disease increased.

Walker noted that, for this reason, those suffering from autoimmune diseases might want to reconsider whether the advantages of hormone replacement therapy (for example, in preventing osteoporosis) outweigh the potential disadvantage of increased estrogen in their systems.

Janet Nelson of the University of Washington presented the truly amazing finding that fetal cells get into a mother's bloodstream and can persist in her body indefinitely. These foreign cells can trigger an autoimmune response similar to that experienced by people who receive transplants, something known as "graft versus host" disease.

Nelson found that this mechanism seemed to play a role a group of patients with scleroderma, an autoimmune disease that causes gradual hardening of bodily tissues.

All women who have been pregnant-healthy ones too-have a few of their children's cells floating around in them. Whether or not an autoimmune response is triggered seems to depend on how closely matched certain genes are, specifically, the gene for HLA, or human leukocyte antigen.

Cells also pass from mother to child during pregnancy, and thus a mother's cells can trigger an autoimmune response in her child. Says Nelson, a woman with children faces a double threat: "Her mother and child can cooperate to mount an attack on her tissue."

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