Nonspecific stimulation of the maternal immune system. I. Effects on teratogen-induced fetal malformations

Background Maternal immune stimulation has reported, but unconfirmed, efficacy for reducing chemical-induced morphologic defects in mice. Methods Teratogenic chemicals (2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD], ethyl carbamate [urethane], methylnitrosourea [MNU], or valproic acid [VA]) were given to pregnant mice to induce cleft palate (TCDD, urethane), digital defects (urethane, MNU), or exencephaly (VA). Before teratogen administration, the immune system of female mice was stimulated by intraperitoneal (IP) administration of pyran copolymer or attenuated bacillus Calmette Guerin (BCG), or by footpad injection with Freund's complete adjuvant (FCA). Results Fetal defects caused by all four chemicals studied were reduced by maternal immunostimulation, sometimes dramatically. In addition to reducing VA-induced exencephaly, immunostimulation with FCA resulted in fetal mice displaying anury (absence of tails). Activated maternal immune cells could not be detected in fetal circulation using flow cytometry and a fluorescent cell-tracking probe. Conclusions For the chemicals tested, maternal immune stimulation has efficacy in reducing fetal defects. Immune protection against teratogenesis may be an indirect effect of maternal immune cell activation. Teratology 62:413–419, 2000. © 2000 Wiley-Liss, Inc.