Detection of small numbers of monoclonal B lymphocytes in the blood of patients with lymphoma.

The definition of complete remission and early relapse in patients with lymphoid malignancy is complicated by the difficulty of recognizing the presence of small numbers of malignant lymphocytes in a population of normal lymphocytes. We have used a method based on the cytofluorometric detection of lymphocytes having homogeneous amounts of surface immunoglobulin of one light-chain class to study blood from patients with lymphomas. The test is capable of reliably detecting 10 per cent or less of monoclonal B lymphocytes in normal blood, and it shows a high incidnece (30 to 40 per cent) of previously unsuspected monoclonal B lymphocytes in patients who were though to have no abnormal blood cells according to standard morphologic technics. The ability to estimate the number of such cells may facilitate the planning of therapy and make more meaningful the concept of complete remission.