Researchers find a key to immunological development

October 18, 2001

PITTSBURGH, Pa. - Children are born with the ability to make antibodies, proteins that fight infection. However, they do not respond to immunization in the same way as adults and several aspects of the immune system are distinctly different. Researchers at the Oklahoma Medical Research Foundation (OMRF) have found another difference, one that may be important to development of the immune system during fetal life.

Lymphocytes, the cells responsible for making antibodies, are made in large numbers throughout life within bone marrow. A variety of evidence suggests that this process is regulated in a negative way by hormones, including estrogen. When estrogen levels are high, as they are during pregnancy, lymphocyte production is severely depressed in the mother's bone marrow. It has been a mystery why the high estrogen concentrations do not also prevent development of the baby's immune system.

Dr. Hidyea Igarashi and his colleagues at OMRF may have solved this paradox. Estrogen controls lymphocyte formation, and thus replenishment of the immune system by binding to hormone receptors found only in rare "precursors" within adult bone marrow. Igarashi found that the receptors were not expressed on corresponding cells of the fetus. Indeed, the receptors are expressed after birth in experimental animals and man. By lacking these receptors, the immune system of the fetus is protected from estrogen and related compounds that might be present in the environment. It adds to information that various kinds of "stem" cells may not be the same in fetal and adult life.

Paul W. Kincade, Ph.D., the head of the research team, will present detailed findings of this research, "Sex Steroids Regulate Lymphocyte Development in Adults, but not Fetal Life and Can Be Used to Resolve Early Blood Cell Precursors," at the upcoming conference, Genomes and Hormones: An Integrative Approach to Gender Differences in Physiology. The conference is being sponsored by the American Physiological Society (APS) and will be held October 17-20, 2001, at the Westin Convention Center, Pittsburgh, PA.

Other investigators in Dr. Kincade's lab have found that hormones can be used as experimental tools for understanding how the various types of specialized blood cells are made from stem cells within bone marrow. His research team's efforts are supported by grants from the National Institutes of Health (NIH).
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The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

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APS Newsroom @
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October 17-20, 2001
Tel: 412.281.3700 (The Crawford Room)

American Physiological Society

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