Monoclonal B-lymphocytes in peripheral blood of patients with plasma cell myeloma. Relation to activity of the disease.

Antisera were produced in rabbits against idiotypic determinants of the myeloma protein from 3 patients with IgG-k myeloma. The antisera did neither cross-react nor react with normal immunoglobulin (Ig). Idiotypic Ig-structures were demonstrated by indirect immunofluorescence (IFL) on 70-94% of peripheral B-lymphocytes inuntreated patients. The total numbers of circulating B-lymphocytes were increased with a simultaneous decrease of T-lymphocytes. Only one of the patients had blood lymphocytes which stained for cytoplasmic Ig with idiotypic antiserum. The monoclonal lymphocyte population decreased gradually during treatment. Plasma cell counts in bone marrow, IgG concentration in serum and erythrocyte sedimentation rate decreased simultaneously, whilt the haemoglobin concentration increased. Very few monoclonal lymphocytes were present during remission. Later, the monoclonal lymphocyte population began to increase in 2 of the patients in parallel with clinical signs indicating relapse. It is concluded that presence of monoclonal B-lymphocytes indicates dissemination of the disease and that they may belong to the malignant cell clone.