[Biclonal gammopathies: clinical and theoretical aspects].

Monoclonal gammopathies are disorders in which a clone of lymphocytes arising from a common ancestor cell proliferates and secretes a monoclonal antibody. Electrophoresis of plasma proteins is used as a diagnostic test for these disorders. It produces a narrow peak within the zone of gammaglobulins, corresponding to the monoclonal antibody. On rare occasions electrophoresis produces 2 narrow peaks simultaneously, suggesting the existence of 2 monoclonal antibodies, establishing a biclonal gammopathy. We present 4 such patients with biclonal gammopathy. The prevalence of mono- and biclonal gammopathies in the general population ranges between 1-3%, but only 1% of these are biclonal. Patients with biclonal gammopathy do not differ clinically from those with monoclonal gammopathy. Theoretically, pathogenesis of biclonal gammopathies might involve true biclonicity: 2 separate transformations in 2 precursor cells. Alternatively, the 2 transformed clones might have originated from a common ancestor cell early in differentiation, prior to immunoglobulin gene rearrangement; in this case pseudobiclonicity could be implied. The question of true biclonicity versus pseudobiclonicity has been examined by others using statistical analysis of isotypic combination distributions of heavy and light chains. The incidence of identity of the light chain isotype in both monoclonal antibodies (44%) was higher than would be expected in a random distribution (27%). In a study of the 2 monoclonal immunoglobulins, the identity of the amino acid sequences of the variable site was demonstrated, suggesting a common ancestor. In another research, anti-idiotypic antibodies suggested a common idiotype in the 2 proteins. Immunofluorescent labeling of bone marrow cells produced conflicting evidence of biclonicity in several studies.(ABSTRACT TRUNCATED AT 250 WORDS)