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."
