Intracellular “Monoclonal” Immunoglobulin in Non-secretory Human Myeloma

A few well documented cases of multiple myeloma without any monoclonal immunoglobulin in either serum or urine have been reported (1–5). The incidence of such cases is about 1% of myeloma patients (1). Whether in such instances the neoplastic plasma cells do not synthetize or do not secrete immunoglobulin has not yet been established with convincing evidence. We have been able to demonstrate by immunogluorescence in four such cases the presence within the plasma cells of non-secreted monoclonal immunoglobulin. All the patients presented as clinically typical myeloma with osseous lesions and infiltration of their bone marrow by an abnormal number of plasma cells. The sedimentation rate was normal or only slightly elevated. There was no cryoglobulin. Repeated paper and agar gel electrophoresis of the serum never showed any narrow band. Urine samples were repeatedly examined. They contained only trace amounts of protein and no Bence Jones protein was detectable. Electrophoresis of 100 × concentrated urine (by negative pressure dialysis in Visking 8/32 membranes) showed no homogeneous component. Immunoelectrophoretic analysis of serum and concentrated urine with a variety of antisera specific for γG, γM, γA, κ and λ showed no abnormal immunoglobulin precipitin lines. It should be emphasized that, in two of the four patients, there was no or only slight decrease in serum γ globulin concentration on electrophoresis. Quantitative immunoglobulin determinations (Table I), performed by the radialimmunodiffusion technique, showed that in these two sera the concentration of γG was within normal limits. Although possibly fortuitous, this finding is in contrast with the profound decrease in normal immunoglobulin level in most cases of secretory multiple myeloma.