Pregnancy and autoimmune disease

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Women's Health Conditions

DOES PREGNANCY HOLD THE KEY TO AUTOIMMUNE DISEASES?

It's no shocker that pregnancy changes a woman's body. Still, sagging breasts, wider hips and bigger feet aren't the only remnants of pregnancy. Long after the cord is cut, a baby's cells can remain inside the mother's body, permanently changing her genetic blueprint.

Studies have shown that fetal cells can persist in a woman's body for decades after giving birth. Conversely, maternal cells often live in a child's body well into adult life. Many researchers believe that understanding how a woman's immune system responds to these 'foreign' cells may help unlock the mysteries of autoimmune disease.

The immune system normally springs to action when bacteria, viruses and other unfamiliar cells invade the body. Yet in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis and lupus, the body attacks its own healthy tissue. For unexplained reasons, more than 75 percent of autoimmune diseases occur in women, primarily during the childbearing years. A slew of other sex differences exist including the fact that multiple sclerosis typically progresses more quickly in men than in women.

In an effort to explain these sex differences, scientists have investigated the effect of pregnancy on these disorders. Depending upon the illness, pregnancy may improve, aggravate or trigger autoimmune disease. For example, rheumatoid arthritis and multiple sclerosis often subside during pregnancy, but worsen or occur for the first time soon after giving birth. Results of a number of recent studies suggest that a fetus' invading cells may trigger these pregnancy-associated changes.

In order for the immune system to defend against trespassers it must be able to distinguish between self and non-self. A group of molecules called the human leukocyte antigens (HLA) play a major part in this making this distinction. Most cells have HLAs on their surfaces that are unique to each person. When the immune system sees cells with foreign HLAs, it attacks.

Autoimmunity: baby versus mother?What happens when a pregnant women is exposed to her baby's unfamiliar HLAs? J. Lee , MD and colleagues from the Fred Hutchinson Cancer Research Center in Seattle theorized that women harboring fetal cells that are very HLA-similar but not identical to their own cells might be at an increased risk of an autoimmune disease called scleroderma. Dr. hypothesizes that these cells might confuse the woman's immune system. She studied 136 people from 21 scleroderma families and compared them with individuals from healthy families.

The researchers discovered that if the mother's HLAs match some of her child's, she was nine times more likely to develop scleroderma. In other words, women who had children who 'looked' a lot like self to the mothers’ immune systems were more likely to develop this autoimmune disease. Dr. theorizes that the resemblance allows fetal cells to escape the mother's immune system for a while and in the end triggers an autoimmune attack. The findings were published in the Journal of Reproductive Immunology.

In related research, Dr. examined the blood of mothers with scleroderma and compared it to that of healthy mothers. She found that scleroderma sufferers had more than 20 times as many fetal cells in their blood than healthy mothers. In addition, Dr. recently found fetal cells in various organs of women with scleroderma, most often in the spleen. These findings add to a growing body of evidence implicating fetal cells in autoimmune disease.

It is important to note that many healthy women also carry fetal cells in their blood. Thus, Dr. proposes, these residual cells may also have potentially beneficial or harmless effects. theorizes that the effects of fetal cells may depend upon how similar or different they are from the mother's cells.

What about hormones?In the past, many researchers blamed fluctuating hormones for pregnancy-induced changes in a woman's vulnerability to autoimmune disease. And while they are undoubtedly involved, they may be just a piece of the puzzle. D. Lockshin, MD, director of the Barbara Volcker Center for Women and Rheumatic Diseases, Cornell University, believes that the interaction between a woman's immune system and her environment is an important area that has been largely understudied.

"Hormones are unequivocally involved [in the sex differences], said Dr. Lockshin, "They are, however, in my belief part of the process, not the cause. Hormones may modulate, not trigger changes in a woman's immune response." Lockshin, like , theorizes that the answer lies in the reaction of a woman's immune system to her environment.

Still a mysteryWhile interesting and thought provoking, Dr. 's findings do not provide proof that fetal cells cause autoimmune disease changes in pregnancy. And exactly why women are more prone to developing autoimmune disease remains a mystery. Accumulating evidence does suggest that the cells that travel from mother to child and vice versa may trigger these diseases. Yet many more, large well-designed studies are needed to clearly define their role in autoimmunity. Furthermore, research suggests that hormones and genetics are also involved in explaining women's susceptibility to autoimmune illnesses.

Sophia CariatiSociety for Women's Health ResearchNovember 29, 2001Sophia Cariati is a medical and science writer with a bachelor's ofscience degree in biology and a master's degree in scientific andenvironmental reporting.

Source: JL. HLA relationships of pregnancy, microchimerism and autoimmune disease. J Reprod Immunol 2001 Oct-Nov;52(1-2):77-84.