Intracytoplasmic and surface-bound immunoglobulins in "nonsecretory" and Bence-Jones myeloma

Immunoglobulins were studied at the cellular level by direct immunofluorescence in twenty-five patients with 'nonsecretory' myeloma and thirty-six patiens with Bence-Jones (BJ) myeloma. The results were compared with those obtained in a control group of thirty-six patients with common secretory myeloma. A monoclonal Ig (IgG in eighteen, IgA in three and kappa chains only in three cases) was found in the cytoplasm of the plasma cells from all the patients with 'nonsecretory' myeloma, with a striking dysbalance in the staining brightness for the heavy and the light chains. A similar dysbalance in staining was also observed for plasma cell surface Ig chains but in the opposite way. In twenty patients with BJ myeloma studied for cytoplasmic Ig only, determinants of a heavy chain were clearly found in four cases. When surface Ig were studied also, the production of gamma chains in addition to the light chain could be ascertained in six of sixteen cases. In addition, IgM with the same light chain type as the BJ protein was detected at the cell surface on plasma cells and lymphocytes in two of these sixteen patients. 'Monoclonal' populations of B lymphocytes bearing the same Ig chains as those produced by the myeloma cells were detectable in five of eleven 'nonsecretory' myeloma and in five of sixteen BJ myeloma patients. Normal blood B lymphocytes were in decreased number, particularly when a 'monoclonal' lymphocytic population was detected. Data are discussed which suggest that plasma cells from most patients with 'nonsecretory' myeloma might synthesize and secrete Ig molecules with structurally abnormal chains that are then quickly degraded.