IGG1-KAPPA BICLONAL GAMMOPATHY ASSOCIATED WITH MULTIPLE-MYELOMA SUGGESTS A REGULATORY MECHANISM

Multiclonal gammopathies associated with multiple myeloma may result e ither from a neoplastic transformation of a cell clone undergoing immu noglobulin class switching or from independent transforming events yie lding proliferation of unrelated plasma cell clones. The simultaneous presence of more than one neoplastic clone may possess regulatory impl ications in terms of cell proliferation, clonal expansion, secretion o f M-components or response to chemotherapy We report a patient, diagno sed with multiple myeloma stage ma, who presented with two well-define d homogenous IgG1-kappa components in the serum (designated WER-1 and WER-2) with striking differences in their plasma concentration and res ponse to the classic melphalan/prednisone treatment. Immunochemical ch aracterization and amino terminal sequence analysis of both the heavy and light chains of each M-component undoubtedly determined their bicl onal origin, WER-1 was identified as IgG1(VHII)-kappa 1 while WER-2 wa s classified as IgG1(VHIII)-kappa III. The plateau phase was character ized by very low or undetectable levels of WER-2, a high, almost const ant, concentration of WER-1 and the absence of Bence Jones protelnuria , whereas these parameters were completely reversed during the escape phase with levels resembling those observed at the time of diagnosis, The statistically significant negative correlation between the biclona l components and the different susceptibility to the treatment clearly suggests regulatory interactions between the clones WER-1 and WER-2.