Peripheral blood B lymphocytes in multiple myeloma.

Multiple myeloma (MM) is a disease of terminally differentiated B lineage cells and thus alterations in circulating B cells may be anticipated. We studied peripheral blood B cells by flow cytometry in 45 untreated MM patients and compared the results to 25 age-matched controls. The total lymphocyte count and the absolute number and percentage of CD20+ cells were significantly decreased in MM patients. Analysis of the relative amounts of CD20+ cells expressing surface immunoglobulin kappa or lambda light chain isotype did not show either clonal B cell excess or light chain isotype suppression. The percentages of CD10+ and CD20+10+ cells were low both in MM patients and in controls. We consider that the CD20+ cells analysed in this study mainly consisted of normal polyclonal B cells. However, the percentage of the CD20+ cells in the peripheral blood of MM patients was a prognostic factor for survival, both as a continuous and as a dichotomized variable.