Detection of Monoclonal B Lymphocytes in Multiple Myeloma by Immunofluorescence Tests of Surface Immunoglobulins

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Abstract
Peripheral blood lymphocytes of 16 patients with a secretory type of multiple myeloma and 5 with nonmyelomatous monoclonal gammopathy were investigated for the surface immunoglobulins [Ig] on the cell by immunofluorescence. A low pH shock of the cells before staining was applied to dissociate the passively adsorbed Ig present on the cell surface. Increases of B [bone marrow-derived] lymphocytes bearing surface Ig which had the same L chains as those of monoclonal Ig produced by the plasma cells were found in 5 of 11 common secretory myeloma patients and in all of 6 Bence-Jones myeloma patients. Ratios of cells bearing L chains of .kappa.- and .lambda.-types (.kappa./.lambda.) appeared abnormal in almost all with an exception of only 3 cases of myeloma patients, even in the cases where the number of Ig-bearing cells did not increase. Increases of possible monoclonal B cells bearing IgG, in addition to IgA cells, were observed in some patients with IgA myeloma. Increases of B cells bearing certain heavy chains were also observed in all 5 patients with Bence-Jones myeloma during the course of disease. No abnormalities of B cells bearing surface Ig were found in nonmyelomatous monoclonal gammopathy. Proliferation of monoclonal B lymphocytes, which may be progenitors to the malignant plasma cells, apparently occurs in a majority of myeloma patients, but not in nonmyelomatous monoclonal gammopathy.