Cells from a fetus can live on in the mother’s body for decades after pregnancy. Likewise, a mother’s cells can also survive for many years in her child. A review of this happening and its consequences were recently published in a prestigious scientific journal.

In some cases, the cells exchanged between the maternal and fetal circulation may not be harmful and may act as “stem cells” serving as an uncommitted source of other types of cells. However, evidence is beginning to develop that in some instances the exchanged cells may be the cause of immune disorders. It has been known for a long time that fetal cells enter the maternal circulation; however, they usually disappear shortly after birth. That they can persist is a surprise. Several studies have shown that women with what are known as autoimmune disorders (allergic to the body’s own cells) are more likely to have fetal cells in their circulation than healthy women.

One such autoimmune disorder is scleroderma, (a severe thickening of the skin, often accompanied by arthritis). It occurs more often in women that men and more often in women who have been pregnant. In a recent study, women with scleroderma had 30 times more fetal cells in their blood than did women without scleroderma. The risk of developing scleroderma in women with fetal cells is 9 times greater than those of the general population. The maternal immune system reaction against fetal cells may be a major factor in causing scleroderma in some women.

Another autoimmune disorder of women is a form of thyroid disorder that reduces the production of thyroid hormone (Hashamoto’s Thyroiditis); it also occurs in some women who have fetal cells for an extended period of time after delivery of the infant. Finally, preeclampsia is associated with an increase in the presence of fetal cells in the maternal circulation. If there is a cause and effect relationship, detecting their presence could give early warning of this dangerous condition of pregnancy which usually occurs in the last 3 months of pregnancy.

Children with maternal cells in their circulation can also be at greater risk of disorders. Several autoimmune disorders of a child’s muscles are now recognized to be associated with the presence of maternal cells in their circulation: an example is dermatomyositis (muscle inflammation associated with a skin rash). A specific gene associated with this disorder has been identified in the child; the gene may be activated by the maternal cells. Other muscle disorders are also characterized by the presence of maternal exchanged cells in the child.

Comment:

Exchanged cells are foreign cells in a women’s or child’s circulation. The presence of exchanged cells in the circulation may be a stimulus in some children and adults for the initiation of a disease process, the autoimmune disorders. However, many people have been found to have foreign cells in their circulation, but do not appear to have any disorder. The questions that still require answers include: Why does the presence of foreign cells appear to be associated with diseases in some people (autoimmune disorders), but not in others? What role, if any, in the disease process do these cells play? Does the presence of maternal foreign cells in the fetus or infant have any effect on its developing brain?

United Cerebral Palsy Research & Educational Foundation, October 2002