Mom's Cells Prime Fetal Immune System

Dec. 5 -- THURSDAY, Dec. 4 (HealthDay News) -- During pregnancy, many of the mother's cells enter the fetus and produce immune cells that prevent the growing baby from rejecting its mother, new research shows.

This finding shows that the two coexist by making the fetus' immune system able to tolerate foreign antigens and could lead to new techniques in stem cell treatments and ways to deal with chronic infections, researchers say.

"The fetal immune system may be considerably more active than previously thought, and a better understanding of fetal immunity may help us to better understand a range of health concerns including fetal infections and autoimmunity," said lead researcher Jeff Mold, a graduate student in the Division of Experimental Medicine at the University of California, San Francisco.

"The findings also suggest that the fetal immune system may be a good target for vaccination strategies aimed at promoting immunological tolerance in human beings," he said.

Modifying the immune system could be important in treating autoimmune diseases, in which the body attacks its own cells, and in preventing organ transplant rejection, where the body rejects the transplanted tissue, the researchers noted.

In addition, the finding may also be important in developing treatments for infectious diseases such as HIV.

"Only 5 to 10 percent of babies born to untreated HIV-infected mothers in the absence of antiretroviral interventions are born infected with HIV. Perhaps some aspect of the immunological tolerance of the fetal immune system explains how the baby could avoid HIV infection in utero," study co-author Dr. Joseph M. McCune, head of the Division of Experimental Medicine, said in a statement.

This study opens up new avenues of research that could be important in developing effective HIV vaccines, McCune noted.

The report was published in the Dec. 5 issue of Science.

In experiments with human tissue, the researchers found that maternal cells were present in the developing fetal lymphoid tissues early in pregnancy when the fetal immune system is first developing, Mold said.