Kinetics of circulating B lymphocytes in human myeloma

The tritiated thymidine labeling index (LI%) of peripheral B lymphocytes was studied in eight myeloma patients using simultaneous immunofluorescence and autoradiography. The LI% values were low (0.3%- 5.1%), but significantly increased as compared to normal controls. In addition, there was excellent correlation between the LI% values and myeloma disease activity: lowest LI% values were observed in remission patients and the highest at the time of relapse. Simultaneous LI% evaluation of bone marrow myeloma cells in five patients gave concordant results, indicating the same kinetic behavior in both these compartments, particularly in the relapse phase. These data indicate both that circulating B lymphocytes include the neoplastic clone and that these B lymphocytes and bone marrow myeloma cells have similar kinetics.