The presence in human serum of a circulating soluble leukemia inhibitory factor receptor (sgp190) and its evolution during pregnancy

The specific binding of leukemia inhibitory factor (LIF) or oncostatin-M (O SM) to transmembrane gp190 or gp130 leads to their oligomerization which is necessary for signal transduction. Although, sgp190 and sgp130 counterpart s also exist, their biological significance remains to be determined. Inter estingly, sgp190 forms have been identified in large amounts in normal mous e sera but so far not in human sera. During gestation, murine sgp190 increa ses 20-fold to 30-fold, while sgp190 RNA levels increase mostly in the live r, uterus and placenta. Sandwich ELISAs were used to detect the presence an d follow the evolution of LIF concentrations and its sgp190 receptor subuni t in the sera of healthy pregnant and non-pregnant women. The LIE concentra tions in whole blood of pregnant women were significantly lower than those of non-pregnant nomen, whereas they returned to these latter values soon af ter delivery. In 51 non-pregnant women, the mean sgp190 concentration was 4 .3 +/- 0.3 ng/ml. It rose slowly but steadily, increasing 3-fold from the 4 th to the 34th week of amenorrhea, at which time, it accelerated more rapid ly until reaching 41 weeks of amenorrhea, 12 times the mean control value. Several hours prior to delivery, the sgp190 concentration dropped sharply b efore returning to control levels 2 days later. The marked increase of sgp1 90 measured in pregnant women extends to humans the observation previously made in mice and suggests a pivotal role for this cytokine system not only during implantation and early embryo development but also throughout pregna ncy and more specifically in the biological function of placenta.