FETAL cells that pass into the mother鈥檚 body are especially common in
diseased tissue. But it鈥檚 not clear whether the fetal cells are causing the
diseases. They might even be replacing damaged tissue.
Three years ago, researchers found that fetal cells can cross the placenta
and persist in the mother鈥檚 body for up to 27 years. Now Bharata Srivatsa and
his colleagues at the New England Medical Center in Boston have found the
descendants of such cells can not only differentiate to form specialised
tissues, but also seem to clump together in diseased tissue.
Foreign cells can trigger an immune attack, just as organ transplants can
trigger immune rejection. Researchers have wondered if fetal cells might be
involved in autoimmune disorders such as lupus and scleroderma, which strike
women more often than men.
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So Srivatsa鈥檚 team looked for male cells in thyroid samples from women with
autoimmune diseases. As controls, the researchers also looked at samples from
women who had been suffering from other disorders, including cancer and goitre.
To their surprise, they found male cells in the controls as well.
Of 29 women, 16 had male cells in their thyroid tissue. No male cells were
found in seven normal thyroid samples taken during autopsies.
The researchers located male cells in the women鈥檚 tissue by staining the
samples with a marker for the Y chromosome. They usually appeared in clumps of
eight to ten cells, but one woman had clumps of up to 200 male cells that had
formed thyroid follicles. This means that the fetal cells had differentiated
inside the woman鈥檚 body.
So what are these cells doing, and why are they more common in diseased
tissue? The cells could play a role in a wide range of diseases, not just
autoimmune disorders, says Srivatsa. On the other hand, they might be there to
repair an injury. The fetal cells may become activated only in response to a
disease state, he suggests.
Mothers are not the only ones who could be affected. Maternal cells can also
enter fetuses and persist for decades.
