FLOW CYTOMETRIC DETERMINATION OF LEUKEMIA-ASSOCIATED MARKER COMBINATIONS FOR THE STUDY OF MINIMAL RESIDUAL DISEASE

To study the minimal residual disease in acute leukemia patients we us ed some marker combinations related either to the simultaneous surface membrane and cytoplasmic marker expression, or to the expression of a typical marker combinations, that are absent or extremely rare in norm al hematopoietic cells. We investigated to which extent flow cytometri c analysis of leukemia-associated marker combination may contribute to sensitive follow-up in patients with acute leukemia. For this purpose dilution experiments were performed, in which artificial mixtures of normal peripheral blood lymphocytes and leukemia cells from a patient with leukemia-associated phenotype were prepared and analyzed for doub le positive cells. Our results showed that the sensitivity of double c olor immunofluorescence assay was 3 in 10(4) cells. Sequential studies of residual disease were evaluated in five acute leukemia patients wi th leukemia-associated markers combinations at diagnosis. In three of them morphologic relapse was preceded by the immunologic detection of small amounts of leukemia cells, while in two other cases, in which no double positive cells for leukemia-associated markers were found, pat ients are still in hematologic remission. This approach to the study o f minimal residual disease could be valuable in monitoring the efficie ncy of chemotherapy, as well as in evaluating the quality control of b one marrow before autografting. Furthermore, flow cytometric approach can efficiently complete other methods, which are used for more exact definition of remission in acute leukemia patients.