We will carry out an immunological analysis of sarcoma specific antigens of avian and murine tumors using mono-clonal and hybridoma antibodies. Such antibodies will be used to probe the diversity of the sarc gene products in the avian retrovirus system. As part of this research, a library of mono-clonal antibodies against sarc gene products and antigens specific to the sarcoma cell will be built up. Among other things, these antibodies could be critical for elucidation of the conserved versus variable regions of the sarc gene. Such information may help determine if: a) the sarc products are a family of related molecules, b) what portions of the molecule are critical for initiation and/or maintenance of transformation.