Idiotype in myeloma terminating in erythroleukemia.

A patient with multiple myeloma, IgG kappa type, developed erythroleukemia with cytogenetic abnormalities three years after diagnosis. The latter disease progressed terminally to acute granulocytic leukemia. Anti-idiotype antibody reagents were prepared by injecting rabbits with the purified monoclonal IgG kappa obtained from the patient's serum and subsequent absorption of the antisera with normal IgG coupled to Sepharose 4B. These reagents reacted specifically with autologous myeloma cells but failed to react with all tested allogeneic cells: these included myeloma cells, reactive lymphocytes and plasma cells, and established lymphoid cell lines. Common idiotypic determinants were found in lymphoid and plasmacytic cells of the patient's marrow, spleen, lymph node, and gastrointestinal tract at autopsy that were not present in the leukemic population. The findings indicate that myeloma and granulocytic leukemia cells have separate clonal origins.