In view of the central role of T lymphocytes in the pathogenesis of rheumatoid arthritis, identification and characterization of unique and functionally important surface antigens on rheumatoid synovial T cells is of considerable interest. To this end, a series of murine monoclonal antibodies will be generated against rheumatoid synovial T cells and against lines and clones derived from such T cell populations. These antibodies will be screened using flow cytometry techniques in order to identify particular antibodies recognizing either T cell specific activation antigens, synovial T cell antigens, or T cell antigens expressed preferentially in rheumatoid arthritis. Such monoclonal antibodies will then be used to biochemically and functionally characterize the specific T cell surface structures they identify. Monoclonal antibodies generated using this approach, as well as previously developed antibodies recognizing T cell differentiation and activation antigens, will be used to analyze a variety of synovial lymphocyte populations. Antibodies generated in this manner should serve as novel probes of the immunopathogenesis of rheumatoid arthritis, and could ultimately be useful as diagnostic and therapeutic tools.