THE TRANSFER OF INTERLEUKIN-8 ACROSS THE HUMAN PLACENTA PERFUSED IN-VITRO

Objective: To assess the placental transfer of interleukin (IL)-8 in v itro. Methods: Eighteen placentas obtained immediately after delivery were perfused with a mixture of I-125-labeled IL-8 (IL-8) and unlabel ed IL-8 in two different concentrations. Antipyrine was coinfused in a ll experiments as a reference compound. Fetal-to-maternal and maternal -to-fetal perfusions were performed. Radioactivity was measured in a g amma counter at the end of each perfusion experiment. In four experime nts, unlabeled IL-8 was analyzed in addition to labeled IL-8 to exclud e a change in the IL-8/IL8 ratio resulting from membrane transfer. Re sults: Two of the 18 experiments had to be discarded because of poor t ransfer of antipyrine. There was only faint accumulation of radioactiv ity in the transplacental compartment, regardless of whether the test substance was added maternally or fetally. Because measurement of unla beled IL-8 yielded negative results, the radioactivity is clearly attr ibutable to free iodine 125, which is generated during IL radiolabelin g or which disassociates from IL-8 in small amounts after radiolabelin g. Conclusion: Interleukin-8 does not appear to cross the placenta by simple diffusion, regardless of the concentration or the perfusion rat e. The impermeability of the placenta to the diffusion of IL-8 might e xplain why there is insufficient correlation between serum and amnioti c fluid cytokine concentrations of pregnant women and the presence of the amnion infection syndrome.