Preeclampsia is a relatively common condition that occurs during pregnancy and it holds significant risks for both mother and child.
Although poorly understood, a study published today finds clues in the immune system that may help to design effective treatments.
Preeclampsia is also referred to as toxemia and pregnancy-induced hypertension.
It occurs in an estimated 5 to 8 percent of pregnancies and is characterized by high blood pressure, swelling in the hands and feet, and high protein levels in the urine.
Certain women are known to be more at risk, including women who have had preeclampsia previously, mothers of multiple babies, and women who are obese.
However, despite being recognized more than 2,000 years ago, the exact causes of preeclampsia are yet to be uncovered.
If not found soon enough, preeclampsia can lead to eclampsia, “one of the top five causes of infant and maternal illness and death.”
Complications include bleeding, blood clots, seizures, and organ failure. The impact to the fetus includes growth restriction and potential hypoxia.
Eclampsia causes 18 percent of maternal deaths in the United States and is the number one cause of premature births.
There are no effective treatments for preeclampsia and the only way to relieve the condition is for the mother to give birth.
This is not always the safest option, as Denise Cornelius, first author of the current study, explains:
“Currently, the only 'cure' for preeclampsia is delivery of the fetus and the placenta, at which time, the hypertension [high blood pressure] and other symptoms of preeclampsia remit. However, early delivery of the fetus results in greater morbidity for the child in the long-term.”
Preeclampsia and the immune system
Because of the sobering statistics behind preeclampsia and because treatment options are severely limited, research that attempts to understand this condition is vital.
Researchers from the University of Mississippi Medical Center recently embarked on a study investigating the role of the immune system’s natural killer cells in the development of preeclampsia.
They presented their results this week at the American Physiology Society’s annual meeting at Experimental Biology 2017 in Texas.
Natural killer cells are a type of lymphocyte, or white blood cell. They provide a rapid immune response and play an important role in the body’s defense against virally infected cells and tumors.
The research team found that natural killer cells “activate and change in response to placental ischemia” – a reduction of blood to the placenta.
Placental ischemia is thought to be one of the early events in the development of preeclampsia, and working out why it occurs in the first place is important for understanding the condition as a whole.
The researchers found that removing these altered natural killer cells helped to reduce the effects of some of the complications of the condition. According to Cornelius:
“Our current study demonstrates that NK cells are activated and altered in response to placental ischemia. We also found that upon deletion of this altered population of cells in an animal model of preeclampsia, hypertension, inflammation, and fetal growth restriction are blunted.”
These findings build on Cornelius’ earlier research, which also looked at the immune system’s role in preeclampsia.
It seems that imbalances in components of the immune system play a substantial role in the development of preeclampsia.
Her earlier projects confirmed that, as preeclampsia develops, certain pro-inflammatory T cells increase in number and T regulatory cells decrease. This imbalance leads to elevated levels of molecules such as inflammatory cytokines.
It is hoped that these new insights might provide a new target for future preeclampsia treatments. If the symptoms of preeclampsia could be successfully and safely reduced with immune-modulating drugs, it might allow more pregnancies to safely continue to full term, thereby improving survival and health outcomes for both the mother and child.