['The objective of the study was to test the hypothesis that factors circulating in the plasma of pregnant women and women with preeclampsia activate monocytes.', 'Blood samples were taken from patients with early-onset severe preeclampsia (n = 9), healthy pregnant women (n = 9), and healthy nonpregnant women (n = 9). A monocytic cell line was incubated with the plasma for 4, 16, and 24 hours. After the incubation, reactive oxygen species (ROS) production and intercellular adhesion molecule (ICAM)-1 expression (protein and messenger ribonucleic acid) were measured.', 'Plasma of both pregnant women and women with preeclampsia, as compared with plasma from nonpregnant women, increased the mean channel brightness (MCB) of ROS after 4 hours of incubation, whereas only plasma of pregnant women increased the percentage of cells producing ROS (after 4 and 24 hours of incubation). Plasma of pregnant women and women with preeclampsia up-regulated the percentage of ICAM-1-expressing cells after 4 hours and down-regulated the percentage of ICAM-1-expressing cells and MCB after 24 hours.'] Does plasma of pregnant and preeclamptic women activate monocytes in vitro?