SEATTLE — April 30, 2008 — Cutting the umbilical cord doesn't necessarily sever the physical link between mother and child. Many cells pass back and forth between the mother and fetus during pregnancy and can be detected in the tissues and organs of both even decades later. This mixing of cells from two genetically distinct individuals is called microchimerism. The phenomenon is the focus of an increasing number of scientists who wonder what role these cells play in the body.
A potentially significant one, it turns out. Research implicates that maternal and fetal microchimerism plays both adverse and beneficial roles in some autoimmune diseases as well as the prevention of at least one cancer. This double-edged sword in turn has opened new avenues of study of the body's immune system and the possibility of developing new tests and therapies.
Two of the world's leading researchers in microchimerism are J. Lee Nelson, M.D., of Fred Hutchinson Cancer Research Center's Clinical Research Division; and V.K. Gadi, M.D., Ph.D., assistant professor of medicine at the University of Washington. Nelson also is a professor of medicine at the University of Washington. Gadi is also a research associate in the Hutchinson Center's Clinical Research Division.
In 2007, they were the first to report these potentially beneficial effects of microchimerism:
Microchimerism reveals its Jekyll and Hyde personality in the case of autoimmune diseases. In the late 1990s, Nelson's group was the first to investigate microchimerism in an autoimmune disease:
The Nelson lab has expanded its study of microchimerism into the fields of reproduction, HIV/AIDS and transplantation. For example, scientists are investigating microchimerism in complications of pregnancy, especially preeclampsia, a disorder characterized by high blood pressure in women in their third trimester of pregnancy, and in recurrent pregnancy loss.
Nelson's group also is investigating maternal microchimerism in patients with HIV and is looking at whether maternal microchimerism levels correlate with whether there is progression or non-progression to AIDS.
Transplantation of stem cells to treat some cancers results in chimerism. Graft-vs.-host disease occurs more often if the cell donor is a woman with prior pregnancies. Tests of female donor cells found they contained male microchimerism, consistent with the interpretation that fetal microchimerism contributes to graft-vs.-host disease. In kidney, pancreas and islet transplantation, Gadi, Nelson and collaborators tested serial serum samples and found that donor-specific microchimerism detection may become a useful non-invasive test for early rejection. This has led to work by several other research groups to therapeutically exploit the principles of naturally-acquired microchimerism in their selection of donors for transplantation.
The discovery that a mother's cells can turn up in her adult progeny and that fetal cells can occur in women who were once pregnant heralds the emergence of microchimerism as an important new theme in biology.
Media Contact
Dean Forbes
Fred Hutchinson Cancer Research Center
(206) 667-2896
dforbes@fhcrc.org
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Fred Hutchinson Cancer Research Center
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