Abstract: This application discloses a novel anti-idiotypic antibody, IMelpg2 and equivalents thereof, as well as, antibody fragments, peptides or antisera capable of reacting with at least one of the idiotopes of: (a) murine monoclonal antibody MEM136 and derivatives thereof; (b) a monoclonal antibody secreted by hybridomas from any species having the same immunological specificity as antibody MEM136; or (c) any polyclonal antibodies from any species having the same immunological specificity as antibody MEM136, wherein (a), (b), or (c) is capable of reacting with a specific determinant (epitope) of a MPG antigen are described, together with their preparation and use in the diagnosis, monitoring and treatment of tumors such as melanoma or other diseased cells that express the MPG epitope recognized by antibody MEM136.

Abstract: B-cell lymphomas express surface immunoglobulin (immunoglobulin) containing unique idiotypic (idiotype) determinants which may be exploited as tumor specific markers. The inventor has produced murine monoclonal antibodies (MAbs) reactive with the idiotype marker derived from 67 patients with low grade, follicular, small cleaved cell lymphoma. Out of 199 monoclonal antibodies, 47 (24%) were found to react with pooled normal human serum immunoglobulin in concentrations ranging from 0.6 .mu.g/ml to 160 .mu.g/ml. Of these 40 monoclonal antibodies, 90% cross-reacted with idiotype present in normal serum in levels <50 .mu.g/ml. Thirty-two of these anti-idiotypes were directed against a shared idiotope expressed on another patient's lymphoma cells. The frequency of shared idiotope expression defined by each antibody ranged from 0.26% to 3.9% of the B-cell lymphomas tested. A panel of five anti-idiotype antibodies reacted with 80% of AIDS associated lymphomas.