Human lymphoid neoplasms, particularly B cell lymphomas, will be studied with the objective of improving taxonomy, detecting minimal disease, furthering understanding of pathogenesis, and improving therapy. Antibody-secreting cells making antitumor antibodies will be cloned and individual clones making desired antibodies immortalized by cell hybridization with non-secreting myeloma cells. This will provide a library of antisera for detecting different types of B cell tumors in man. Together with antisera for detecting different classes of surface immunoglobulin and with the use of the fluorescent activated cell sorter, we will obtain an immunologic "fingerprint" of each tumor and search for clinical correlates of different categories of fingerprints. Secreted products of tumors and responsiveness of tumors to mitogens and T cell signals will also be used for classification. The same tools will be employed to diagnose minimal disease. The presence on B cell tumors of a unique tumor-specific antigen, namely, idiotypic determinants of surface immunoglobulin, allows a study of the role of the anti-idiotypic response in the pathogenesis, prevention, and treatment of experimental and human B cell tumors.