Paraproteinaemia: use of idiotypic determinants as specific markers for tumour activity

Five patients with paraproteinaemia were investigated using anti-idiotype antibodies specific for their paraproteins. Sensitive assays were used to detect soluble paraprotein either in serum or in supernatants from cultures of peripheral blood mononuclear cells (PBMC) and bone marrow cells. It was found that (i) measurement of serum paraprotein by specific radioimmunoassay is a sensitive method of monitoring the course of multiple and solitary myeloma, (ii) morphologically normal bone marrow from a multiple myeloma patient contained paraprotein-secreting plasma cells, (iii) a patient with benign monoclonal gammopathy had at least one stage in her disease where pre-plasmacytic tumour cells were present in the peripheral blood, (iv) the PBMC of the patients with active myeloma contained suppressor monocytes, and (v) PBMC from treated myeloma patients (both those with still active disease and those in apparently complete remission) would not secrete paraprotein in culture under a variety of different culture conditions including partial monocyte depletion.