LEUKEMIA-ASSOCIATED PHENOTYPES - THEIR CHARACTERISTICS AND INCIDENCE IN ACUTE-LEUKEMIA

Leukemia-associated phenotypes have been suggested to be a valuable to ol for the detection of minimal residual disease in acute leukemia pat ients, as they allow to distinguish leukemic blasts from normal hemato poietic progenitor cells. The aim of the present study was to analyze the proportion of acute leukemia patients (both with lymphoid and myel oid leukemias) in which the immunological detection of leukemia-associ ated phenotypes was convenient for the distinction of leukemic and nor mal cells. For this purpose we have studied the blast cells from 186 a cute leukemia patients at diagnosis with a large panel of monoclonal a ntibodies by flow cytometry using double staining combinations. From a berrant phenotypes on blast cells we followed lineage infidelity (coex pression of myeloid markers in lymphoid leukemia cells and vice versa, as well as the simultaneous expression of both, T and B cell markers in one lymphoid blast cell) and asynchronous marker expression (simult aneous expression of early and late markers in one cell). One hundred and five of the 186 acute leukemia cases analyzed (56%) showed the pre sence of leukemia-associated phenotypes. In 41 of the 90 ALL cases fol lowed (46%) and in 40 of the 96 AML, cases studied (42%) lineage infid elity was observed. Asynchronous antigen expression was detected in 24 followed cases (13%). Evaluation of the cell marker density by means of calibration microbeads demonstrated abnormal mean channel immunoflu orescence and molecules of equivalent soluble fluorescein for CD8 in t wo patients with T cell malignancies at diagnosis. Abnormal CD8 densit y might thus represent a characteristic feature of malignant CD8-posit ive T cell clone. Quantitative marker evaluation therefore seems to be another important mean for the detection of aberrant phenotypes on le ukemia cells suitable for the detection of minimal residual disease.