Plasma cell dyscrasias-A comparative study of cell surface properties in plasma cell leukemia and myeloma

Plasma cells from a patient (Cw) with plasma cell leukemia and excretion of large amounts of immunoglobulin λ chains have been studied in vitro. After exposure to PHA most of the plasma cells were transformed to blasts. Using commercial antisera against κ and λ chains for cytoplasmic immunoflourescence, unstimulated and stimulated cells stained with λ chain specific antisera, exclusively. Using an antiserum against the patient's uroprotein, a positive reaction was also observed. These morphological and immunofluorescence findings were in line with the stimulation experiments using 3H-thymidine and 14C-leucine. In contrast, plasma cells which were isolated from the bone marrow of three myeloma patients and from the pleural effusion of a patient with extramedullary plasmacytoma did not respond to PHA. In other experiments, the binding of fluorescein-labelled PHA to the leukemic plasma cells was studied and compared to the binding properties of plasma cells from the bone marrow of a myeloma patient. From the results it is concluded that leukemic plasma cells possibly are distinguished by the presence of N-acetyl-galactosamine residues on their surface. It is speculated that these receptors are responsible for the special migratory properties of leukemic plasma cells. In addition, an attempt was made to characterize leukemic plasma cells by their response to PHA in the presence of actinomycin D. It appeared that the incorporation of 3H-thymidine by these cells is highly resistant to actinomycin D when compared to the results of other authors working with human lymphocytes. The effect of actinomycin D on protein synthesis as measured by 14C-leucine incorporation, however, was similar in both types of cells.