The role of complement in pregnancy-induced hypertensive disease

Preeclampsia is a pregnancy-induced hypertensive disease with an incidence of about 5% in primigravidas and, being common, it significantly contributes to maternal and neonatal morbidity and mortality. The primary cause remains unknown but might be immunologic, since immunologic aberrations are described in preeclampsia. Activation of the complement system in pregnancy-induced hypertensive disease has been discussed during the last 60 years. It is now strongly indicated that complement activation occurs in preeclampsia. The complement system is very potent and one of the major effector pathways of the process of inflammation. The pathological manifestations, endothelial damage and microvascular injury, and thereby the clinical findings in preeclampsia, may be explained by complement activation, resulting in the direct vascular effects of biological active complement components and complement-mediated activation of leukocytes, with release of potent inflammatory mediators. This new etiological hypothesis might give other options in therapy and prevention of pregnancy-induced hypertensive disease.