There is considerable interest in the role of cytokines in pregnancy and the initiation of labor. IL-1β, IL-6, and TNFα have been detected in amniotic fluid late in the second trimester, and levels rise until term. Trophoblasts bear many similarities to monocytes, and they are likely sources of cytokines at the maternal-fetal interface. We examined trophoblast-like JAR cells to determine whether they secrete the cytokine IL-1β with Fcγ receptor cross-linking, as do normal monocytes.

JAR cells were cultured with either BSA- anti-BSA immune complexes or monomeric IgG. After 72 hours, concentrations of IL-1β were measured by ELISA. JAR cells also were incubated with complexes for periods of 30 minutes to 18 hours. Cells were collected and analyzed for the presence of IL-1β mRNA by rtPCR or for IL-1β/IL-1β precursor (pro-IL-1β) by Western blot.

Both monomeric IgG and immune complexes induced IL-1β from JAR cells in a dose-dependent fashion. Levels achieved with immune complexes were nearly twice those achieved with monomeric IgG. For example, at 100 μg ml. IL-1β concentrations induced by IgG were 292 ± 140 pg/ml, while cells incubated with immune complexes produced 429 ± 276 pg/ml IL-1β (p=0.007). Cycloheximide had no effect on the secretion of IL-1β, demonstrating that the secreted protein was preformed. RtPCR and Western blot experiments were consistent with this finding. Neither IL-1β nor IL-1 converting enzyme mRNA's were detected by rtPCR. Western blots showed a 34,000 kD protein which was constitutively expressed and whose levels did not increase with the addition of IgG or immune complexes. The 17,000 kD protein (the active form of IL-1β) was not detected.

We conclude that trophoblast-like JAR cells constitutively express pro-IL-1β which can be released with FcγR stimulation. As increases in amniotic fluid concentrations of IL-1β coincide with the transport of IgG across the placenta, we speculate that Fcγ receptor engagement during IgG transport may alter the immunologic milieu at the maternal-fetal interface and play a role in the events leading to the initiation of labor.