Malignant transformation is accompanied by extensive cell surface alterations. Of particular interest are alterations of histocompatibility antigens, cell surface components which have been implicated in cell-cell interactions in the immune response and in histogenesis. This project will employ serological and immunochemical techniques to characterize cell surface antigens of a series of spontaneous and chemically induced murine tumors. The antigenic profiles of the tumor cells will be analyzed by 2-dimensional electrophoresis of immunoprecipitates. Specific antisera will be used to assess the contribution of fetal and viral antigens to the total antigenic mosaic. Histocompatibility antigens expressed by tumor cells will be subjected to extensive immunochemical analysis in order to detect structural alterations. Immunofluorescence techniques and bivalent crosslinking reagents will be used to examine topographic relationhips between histocompatibility and tumor-associated antigens on the cell surface. Serum from animals bearing tumors will be examined for the presence of tumor associated and histocompatibility antigens. These studies will contribute to our understanding of the structural basis of altered-self recognition in relation to tumor immunity and should provide insight into the role of cell surface structures in regulation of cell proliferation and positional control.