When tissue gafts are transplanted from one species of mollusc to another (xenografts), the grafts reportedly fail, i.e., die. The goal of the proposed research is to understand the mechanisms of xenograft failure in molluscs. Specifically, the study will assess the relative roles of (1) physiological incompatibility between donor and recipient and (2) immunological rejection by the recipient. Methods will include implantation of hearts from phylogenetically close and phylogenetically distant species into a single recipient snail species. Fates of the implants will be followed histologically and histochemically, and will be compared to fates of hearts maintained in vitro, and to fates of implants from donors of the same species. In addition, the role of the immune system will be ascertained by conducting implants in immunosuppressed recipients, i.e., snails infected with larval trematodes. Finally, initial information on the types of determinants on the xenograft recognized as non-self will be gained by subjecting grafts to chemical modification such as neuraminidase digestion and lectin binding prior to implantation. The potential significance of this project is that it may help to elucidate the mechanisms of immune-like self recognition in molluscs, serve as a model for studying primitive forms of self recognition that also occur in vertebrates, and provide information on phylogenetic relationships within an important group of molluscs.
