You Are a Chimera (Thanks to Mom)

Your mother's cells can be a part of you for decades.

By Kathy A. Svitil|Wednesday, May 09, 2007

Red-stained X chromosomes
indicate the presence of
Mom's cells in a boy's
Image courtesy of
PNAS, Vol. 104, No. 5 © 2007
National Academy of Sciences, USA

When a mother says that she is “always with” her children, it is literally true: Scientists recently found that a small number of maternal cells can persist in a woman’s offspring for decades or longer. Although researchers have suspected that maternal cells might play a role in provoking immunologic problems, this study found that in individuals with type 1 diabetes, at least, those cells might actually be lending a helping hand.

Maternal cells, which cross the placenta during pregnancy, can set up residence anywhere in the fetus, including the bloodstream, heart, liver, and thymus gland. The phenomenon, called microchimerism, is thought to contribute to a number of autoimmune disorders, like lupus and rheumatoid arthritis. The idea is that the cells elicit an immune response that spirals out of control, attacking the child’s own tissue.

The cells may be more beneficent in type 1 diabetes, a relatively rare autoimmune form of the disease that usually affects children and young adults. Immunologist J. Lee Nelson of the Fred Hutchinson Cancer Research Center in Seattle took blood cells from 94 diabetes patients, their healthy siblings, and two dozen unrelated adults. More than half the diabetics had maternal DNA in their blood, but only about a third of their siblings and less than 20 percent of the unrelated adults did. While that might seem to implicate the mother cells in the disease, Nelson and her colleagues learned otherwise when they looked at the pancreases, removed during autopsy, of four individuals, including one diabetic. They found maternal beta cells—cells that pump out insulin—in all of them. Microchimerism is, therefore, present in even normal pancreases. Of the beta cells in the diabetic pancreas, however, almost twice as many were maternal cells, which means Mama’s cells may in fact be helping to repair the pancreas. Harnessing the effect could lead to new treatments for the disease. For instance, maternal cells might be transplanted into a diabetic to repair the pancreas. “The hope is that it could potentially stave off the disease,” Nelson says.

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