The goal of this study is to identify, purify and characterize molecules involved in adhesive, migratory and invasive activities of human placental trophoblast cells. For this purpose we will use an in vitro model of human placentation in conjunction with an immunochemical approach proven successful for identifying cell-adhesion molecules in other systems. In the model for placentation, trophoblast cells from first trimester human chorionic placental villi adhere to and invade extracellular matrices in vitro. Villi from second trimester placenta adhere but do not invade, while villi from term placenta neither adhere nor invade. Thus, the in vitro model mimics several features of placentation in vivo, suggesting that the timetable of expression of molecules involved in placentation in vivo has been retained. We propose to produce broad spectrum antisera against plasma membranes from syncytio- and cytotrophoblastic cells of first trimester, second trimester and term human placentas. Antisera will be screened for ability to: 1) perturb adhesive, migratory or invasive behavior of trophoblasts; 2) immunoprecipitate stage-specific antigens. Following the production of useful polyspecific antisera, relevant antigens will be purified and used as immunogens to produce monospecific antisera or monoclonal antibodies. These antibodies will be used for localization studies, efficient large scale purification of antigens for biochemical characterization, and studies of the regulation of expression of their respective antigens in placental tissue at different stages of development. An immunochemical approach to characterizing trophoblast cell behavior in the in vitro model for placentation offers a unique opportunity to address the molecular basis for the adhesive and invasive behavior of human trophoblast cells during implantation. Increasing our understanding of normal trophoblast functions which lead to successful placentation may shed light on the etiology of syndromes (such as preeclampsia) which appear to result from defects in this process. Results of these studies may have relevance as well to other adhesive and migratory processes which are important parameters of early embryogenesis. Finally, since placentation is a self limiting invasive process, understanding how adhesive and invasive processes are regulated during placentation may increase understanding of the unregulated metastatic process.