OBJECTIVE: The aim of our study was to compare the expression of leukocyte adhesion molecules, intracellular reactive oxygen species, and vasoactive substances in preeclampsia and matched normotensive pregnancies and to explore differences between pregnancy and the nonpregnant state regarding these parameters. METHODS: Flow cytometry was used to analyze the monocyte and granulocyte expression of adhesion molecules from 20 matched pairs of preeclampsia/normoten sive pregnancies and 12 nonpregnant subjects. Basal levels of CD11b, CD11c, CD62L, and CD14 were measured. In addition, expression of human lymphocyte antigen-DR, CD4, CD8, and CD4/CD8 ratio were assessed. Basal reactive oxygen species levels, as well as reactivity upon in vitro stimulation with phorbol 12-myristate 13-acetate, were measured in monocytes and granulocytes with the probes dihydroethidium, dichlo-rofluorescein-diacetate, and dihydrorhodamine-123. Further, the plasma levels of endothelin-1, the nitric oxide metabolites nitrite/nitrate, and total antioxidant status were analyzed. RESULTS: Monocytes expressed significantly higher levels of CD11b and CD14 in preeclamptic patients compared with normotensive pregnant subjects, whereas CD11c was elevated on both monocytes and granulocytes in pregnancy compared with the nonpregnant state. Both monocytes and granulocytes displayed higher basal, as well as phorbol 12-myristate 13-acetate-stimulated, amounts of reactive oxygen species in the preeclampsia group compared with the normotensive group. We also found die endothelin-1 and antioxidant levels significantly elevated in preeclampsia patients compared with normotensive subjects, whereas no differences were seen between the groups regarding nitrite/nitrate levels. CONCLUSION: These results show that the maternal blood leukocytes are activated in preeclampsia and support the view that oxidative stress is a contributing factor in the pathophysiolosy of preeclampsia. OBJECTIVE: The aim of our study was to compare the expression of leukocyte adhesion molecules, intracellular reactive oxygen species, and vasoactive substances in preeclampsia and matched normotensive pregnancies and to exploring differences between pregnancy and the nonpregnant state regarding these parameters. METHODS: Flow cytometry was used to analyze the monocyte and granulocyte expression of adhesion molecules from 20 matched pairs of preeclampsia / normoten sive pregnancies and 12 nonpregnant subjects. Basal levels of CD11b, CD11c, CD62L, and CD14 were measured. In addition, expression of human lymphocyte antigen-DR , Basal reactive oxygen species levels, as well as reactivity upon in vitro stimulation with phorbol 12-myristate 13-acetate, were measured in monocytes and granulocytes with the probes dihydroethidium, dichlo-rofluorescein -diacetate, and dihydrorhodamine-123. Further, the plasma levels of endothelin-1, the nitric oxide metabolit RESULTS: Monocytes showed significantly higher levels of CD11b and CD14 in preeclamptic patients compared with normotensive pregnant subjects, whereas CD11c was elevated on both monocytes and granulocytes in pregnancy compared with the nonpregnant state. Both Monocytes and granulocytes showed higher basal, as well as phorbol 12-myristate 13-acetate-stimulated, amounts of reactive oxygen species in the preeclampsia group compared with the normotensive group. We also found die endothelin-1 and antioxidant levels significantly elevated in preeclampsia patients compared with normotensive subjects, but no differences were seen between the groups regarding nitrite / nitrate levels. CONCLUSION: These results show that the maternal blood leukocytes are activated in preeclampsia and support the view that oxidative stress is a contributing factor in the pathophysiolosy of preeclampsia.