Age-related change of distribution of immunoglobulin containing cells in human bone marrow. Changes in patients with benign monoclonal gammopathy and multiple myeloma.

The number and mode of distribution of immunoglobulin containing cells in human bone marrow were investigated immunohistochemically using paraffin sections of bone marrow aspirates. In individuals without specific diseases, the number of immunoglobulin containing cells per unit field in bone marrow increased with advancing age until the 3rd decade and leveled off thereafter. The magnitude of the increase was great for Ig-G and Ig-A, but very slight for Ig-M. Such age-related change in the number of Ig-G and Ig-M containing cells in bone marrow was almost comparable to the age-related change of serum level of Ig-G and Ig-M. However, the magnitude of age-related increase of Ig-A containing cells in bone marrow was apparently higher than that of the serum level of Ig-A. Cluster formation of immunoglobulin containing cells increased with age in terms of both incidence and size. Three points were suggested for differentiation of benign monoclonal gammopathy (BMG) from multiple myeloma (MM). First, the ratio of serum level of M-component divided by the average number of immunoglobulin containing cells per unit field was higher in BMG than in MM; second, the number of cells per cluster of immunoglobulin containing cells was more than 50 in MM, but that in BMG less than 20; third, the small immunoglobulin containing cells with narrow cytoplasm were more prominent in MM than in BMG.