Detection of monoclonal B lymphocytes in multiple myeloma by immunofluorescence tests of surface immunoglobulins.

Peripheral blood lymphocytes of 16 patients with secretory type of multiple myeloma and 5 with nonmyelomatous monoclonal gammopathy were investigated for the surface immunoglobulins on the cell by immunofluorescence. A low pH shock of cells before staining was applied to dissociate the passively absorbed immunoglobulins present on the cell surface. Increases of B lymphocytes bearing surface immunoglobulins which have the same light chains as those of monoclonal immunoglobulins 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 light 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 immunoglobulin were found in nonmyelomatous monoclonal gammopathy. These results suggest that proliferation of monoclonal B lymphocytes, which may be progenitors to the malignant plasma cells, occurs in a majority of myeloma patients, but not in nonmyelomatous monoclonal gammopathy.