All cells-both primary and established cell lines-employed for these studies were cultured in 5% CO 2 /95% air in a 378C humidified incubator. The RAW 264.7, CHO-K1, CHO DHFR À , and BeWo cells were obtained from American Type Culture Collection and cultured in the media and cell densities recommended. Because FBS contains high levels of TGFB1, we used 5% or 10% fetal clone III serum alternative (Hyclone) for culturing cells in the experiments in which TGFB1 was to be measured. The human invasive trophoblast HTR-8/SVneo cell line was provided to us by Dr. Charles Graham (Queen's University, Kingston, ON, Canada) and was cultured in HyQ RPMI 1640-RS (Hyclone) or RPMI 1640 (Gibco) with 5% fetal clone III or FBS, 13 normocin (InvivoGen), and 100 U/ml of penicillin/streptomycin (Gibco) [24] . The trophoblast cell line SGHPL-4 was a kind gift or Dr. G.S. Whitley (Division of Basic Medical Sciences, St. George's University of London, U.K.) and was cultured in Ham F-12 nutrient mix supplemented with either 10% fetal clone III or 10% FBS, 2 mM L-glutamine, and 103 penicillin/streptomycin. The human endometrial endothelial cell line (HEEC) was a gift from Dr. Gil Mor (Yale University School of Medicine, New Haven, CT). HEEC was cultured as described by Aldo et al. [25] and Krikun et al. [26] .