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Immune Response is Uniquely Activated during Pregnancy, Report University of Pittsburgh Researchers

PITTSBURGH, February 21, 2002 — Scientists at the University of Pittsburgh are zeroing in on cellular changes associated with normal pregnancy and what these changes may mean in relation to preeclampsia and other disorders of pregnancy.

What they are finding is that normal pregnancy results in a significant increase in certain key cells that make up the body’s immune response. These cells prepare the mother to fight off infection, yet protect the growing fetus from being rejected as a foreign invader.

"We are the first ones to study immune system alterations during pregnancy in such great detail," said Patrizia Luppi, M.D., a research assistant professor of pediatrics at the University of Pittsburgh School of Medicine. Dr. Luppi is principal investigator of the study, which is being published in the February issue of the American Journal of Reproductive Immunology.

"We think that by helping to define the changes that take place at the cellular level in normal pregnancy, we can learn more about some of the problems of pregnancy, such as preeclampsia, premature labor or miscarriage, also at the cellular level," Dr. Luppi added.

What Luppi and her colleagues found, specifically, was an increase in immune cells known as monocytes and neutrophils -- white blood cells that destroy foreign particles such as bacteria and tissue debris. These immune cells were not only more numerous; they were also far more active than usual, releasing more of the specialized chemical markers that determine interactions among immune cells and between these cells and the walls of blood vessels. Such cellular interactions are vital to immune system defense against infection and disease.

Blood samples collected during the third trimester of pregnancy were compared from 36 women with normal pregnancies and 26 who were not pregnant, Dr. Luppi said.

While some immune system cells increased during pregnancy, others, such as lymphocytes, decreased, the study found. Also a form of white blood cell, lymphocytes produce antibodies. Dr. Luppi and her colleagues are now expanding their study of these alterations during pregnancy by measuring cytokines released by the activated immune cells. Cytokines are proteins produced by immune cells that promote inflammation.

"This is all considered to be part of a generalized inflammatory response," said Dr. Luppi. "A heightened immune response during pregnancy could conceivably protect the mother and baby during gestation, especially from an attack by foreign pathogens. This would explain why pregnant women usually don’t die from infections."

Further studies are needed to track immune response and associated cytokine activity throughout pregnancy, but these novel findings are intriguing, according to Dr. Luppi.

"Defining the immunological profile that occurs during normal pregnancy is the first step," she continued. "We can then compare the immunological changes that take place during a complicated pregnancy for diagnosis."

In addition to providing tools needed to identify women at risk, predict outcomes and formulate possible interventions, this work may provide useful insights into the causes of pregnancy complications, Dr. Luppi said.

In addition to Dr. Luppi, study authors include Massimo Trucco, M.D.; Julie DeLoia, Ph.D.; and Catherine Haluszczak, B.S.