PROBLEM: Communication at the human maternal-fetal interface occurs by an intricate cytokine network. This study examines cytokine expression by normal first-trimester human chorionic villi. METHOD OF STUDY: Tissues were obtained at elective pregnancy terminations (7-9 weeks). Total RNA was isolated from chorionic villi by guanidinium isothiocynate-acid phenol extraction. A reverse transcriptase-polymerase chain reaction technique was used to examine cytokine expression. beta-Actin was used as the housekeeping gene, and mitogen-stimulated lymphocytes served as positive controls. RESULTS: beta-Actin was uniformly expressed by all chorionic villous samples. Interferon (IFN)-alpha and -beta also were highly expressed. Moderate expression was noted for interleukin (IL)-10, IL-6, tumor necrosis factor (TNF)-alpha, and IL-1 beta. In contrast, transforming growth factor-beta 1, IFN-gamma, IL-2, and IL-1 alpha were either weakly expressed or absent in first-trimester villi. CONCLUSIONS: Cytokines may contribute to pregnancy immunotolerance (IFN-alpha, IFN-beta, and IL-10), viral resistance (IFNs), hormone secretion (IL-1 and IL-6), and cellular remodeling (IFN-gamma and TNF-alpha) within the chorionic villous.