Alterations of peripheral blood B-lymphocyte populations in plasma cell disorders

Peripheral blood lymphocytes of patients with multiple myeloma, macroglobulinemia, and monoclonal gammopathy of uncertain significance were analyzed for B cells, and cells bearing kappa light chains and lambda light chains on their surfaces. Compared with controls, the number of B cells were decreased in all three groups. Contrary to other reports, the authors found a B-cell depression of similar magnitude in patients with untreated myeloma and in those with apparently benign monoclonal gammopathy. There was no difference between treated and untreated myeloma patients as a group, or as individuals studied before and after treatment. However, in comparison to control patients, alkylator therapy depressed the leukocyte count, lymphocyte count, and B-cell number both in the myeloma and in the macroglobulinemia groups. All five patients with previously untreated macroglobulinemia had an increased proportion of circulating lymphocytes with surface light chains of the same type as the M protein. Two patients with IgG myeloma-like disorders had increased circulating B cells with monoclonal surface light chains. This study supports the concepts that normal B cells are depressed in plasma cell disorders, and that abnormal B cells, which are apparently monoclonal, do circulate in some cases. Our results are compared with other published data.