The goal of this research is to apply modern technology to the study of schistosome-snail interactions. The techniques to be used include denaturing and nondenaturing slab gel electrophoresis, high-performance liquid chromatography (HPLC), 125I surface-labeling, and various immunological techniques (immunoblotting, monoclonal and polyclonal antibody production, etc.). Such methods either have not been applied or have not been systematically or extensively used to study the three major interacting components comprising the immune association between the vector snail, Biomphalaria glabrata, and Schistosoma mansoni. These techniques will be employed to examine circulating blood cells (hemocytes), cell-free hemolymph (serum), and the sporocyst tegumental surface in an effort to determine the molecular and biochemical parameters determining immune compatibility in this host-parasite system. This first will involve characterizing hemocyte membrane components of resistant (10- R2 strain) and susceptible (PR albino M-line strain) B. glabrata by polyacrylamide gel electrophoresis (PAGE), surface radioiodination, and immunoblotting. Serum also will be examined by PAGE, HPLC and immunoblotting. Next, the S. mansoni sporocyst tegument will be characterized by PAGE, radioiodination and immunoblotting. Finally, in vitro and in vivo experiments will be conducted to identify and functionally analyze surface antigens important in hemocyte-sporocyst binding and cytotoxicity, the significance of acquired host-snail antigens in parasite immune evasion, and important serum factors in parasite recognition and/or cytotoxicity. Results of such studies will provide valuable insights into how immune compatibility is manifested in schistosome-snail relationships. Moreover, the successful application of the proposed techniques will be extremely valuable in the analyses of other parasites and invertebrate vectors of human disease. Thus, the information gained from the proposed research will undoubtedly facilitate how we deal with invertebrate vectors of human disease in the future.