Distribution of immunoglobulin-containing cells in bone marrow and lymphoid tissues in patients with monoclonal gammapathy.

Cell suspensions of bone marrow and lymphoid tissue from 85 patients with monoclonal gammapathy were investigated by a direct immunofluorescence procedure for the detection of intracellular immunoglobulin alpha, mu, gamma, kappa and lambda chains. Serum Ig levels were determined and daily syntheric rates estimated. In all cases the majority of Ig-containing bone marrow cells contained the same Ig class as that of the M-component in serum or urine indicating a diffuse distriubtion of these clones in the bone marrow. This was observed not only in myeloma but also in benign monoclonal gammapathy (BMG) and lymphoma with an M-component. The M-component producing clone could be traced to extramedullary lymphoid tissue in myeloma but usually not in BMG. A positive correlation was found between the calculated synthetic rate of the M-component and the number of Ig-containing cells in the bone marrow and some indication was found that the synthetic rate per cell might be lower in IgM and IgG than in IgA monoclonal gammapathy. The depressed level of polyclonal Ig in myeloma and to some extent in BMG was parallelled by a diminished number of Ig-containing cells in the bone marrow.