EXPERIMENTAL-STUDY OF TRANSPLACENTAL PASSAGE OF ALPHA-INTERFERON BY 2ASSAY TECHNIQUES

Two methods of assaying alpha interferon (IFN-alpha) were compared dur ing an experiment aimed at determining whether IFN-alpha crosses the h uman placenta. Human placentas, collected after delivery following a n ormal pregnancy to term, were catheterized on both sides: fetal and ma ternal. The IFN-alpha was introduced in known amounts in the maternal circulation and was assayed in the efferent fetal fluid. The following two detection methods were used: radioimmunoassay by competition with [I-125]IFN-alpha and assay with a biological system in which IFN-alph a protected Madin-Darby bovine kidney cells from destruction by vesicu lar stomatitis virus. The results obtained by the two methods were in perfect agreement for the efferent fetal fluid samples. They showed th e absence of placental transfer of IFN-alpha. The biological method wa s found to be more sensitive than radioimmunoassay for low IFN-alpha t iters (< 10 IU/ml) but was less reproducible, probably owing to the us e of twofold dilutions. The specificities of the two methods were simi lar and their practicalities were equivalent; the biological method, h owever, was less costly. The study illustrates the complementarity of the two methods, which were based on different principles. The agreeme nt obtained between the two methods provides a clear confirmation of t he experimental results.