Labour-associated expression of intercellular adhesion molecule-1 (ICAM-1) in placental endothelial cells indicates participation of immunological processes in parturition.

Inflammatory cytokines induce or upregulate de novo expression of cell adhesion molecules on endothelial and epithelial cells. In order to demonstrate inflammatory reactions within placental tissues in association with normal term as well as non-infection-induced preterm labour, the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and endothelial leucocyte adhesion molecule-1 (ELAM-1) was examined by immunohistochemical methods in both trophoblastic villi (n=123) and umbilical cord (n=61). As a result, ICAM-1 immunoreactivity was exclusively localized in the endothelial cells of the fetal vascular system, while VCAM-1 and ELAM-1 were not detected. Whereas ICAM-1 was not expressed in early pregnancy (9-12 weeks of gestation), it could be weakly detected at the end of pregnancy in cases of elective caesarean delivery in the absence of labour, and was significantly more strongly expressed in cases of vaginal delivery after spontaneous onset of normal term labour. Significantly increased immunoreactivity of ICAM-1 within umbilical cord tissues was also found in association with uncontrollable preterm labour in the absence of intrauterine infection which was excluded after histological examination of fetal membranes, umbilical cord and chorionic plate. We conclude that ICAM-1 expression in the endothelium of the fetal vascular system is associated with the presence of labour and reflects participation of immune-inflammatory reactions in labour-promoting mechanisms.