The transforming growth factor-beta superfamily cytokine macrophage inhibitory cytokine-1 is present in high concentrations in the serum of pregnant women

Macrophage inhibitory cytokine-1 (MIC-1) is a recently described divergent member of the transforming growth factor-beta superfamily. MIC-1 transcript ion up-regulation is associated with macrophage activation, and this observ ation led to its cloning. Northern blots indicate that MIC-1 is also presen t in human placenta. A sensitive sandwich enzyme-linked immunosorbent assay for the quantification of MIC-1 was developed and used to examine the role of this cytokine in pregnancy. High levels of MIC-1 are present in the ser a of pregnant women. The level rises substantially with progress of gestati on. MIC-1 can also be detected, in large amounts, in amniotic fluid and pla cental extracts. In addition, the BeWo placental trophoblastic cell line wa s found to constitutively express the MIC-1 transcript and secrete large am ounts of MIC-1. These findings suggest that the placental trophoblast is a major source of the MIC-1 present in maternal serum and amniotic fluid. We suggest that MIC-1 may promote fetal survival by suppressing the production of maternally derived proinflammatory cytokines within the uterus.