Immunophenotype of normal and leukemic bone marrow B-precursors in a Brazilian population. A comparative analysis by quantitative fluorescence cytometry

The distinction between normal and leukemic bone marrow (BM) B-precursors i s essential for the diagnosis and treatment monitoring of acute lymphoblast ic leukemia (ALL), In order to evaluate the potential use of quantitative f luorescence cytometry (QFC) for this distinction, we studied 21 normal indi viduals and 40 patients with CD10(+) ALL. We characterized the age-related changes of the CD10, CD19, TdT. CD34 and CD79a densities in normal and leuk emic BM, Compared to normal adults, the B-precursors from normal children e xpressed significantly lower values of CD34-specific antibody binding capac ity (SABC) (median value of 86.6 vs 160.2 arbitrary units (a.u.) in childre n and adults, respectively), No significant age-related difference was obse rved in the expression of the other markers in the normal BM, or in any of the markers in the leukemic BM, Based on the literature, we set the cut-off value for the normal CD10 expression at 45 x 10(3) a.u. for both age group s. For the remaining markers we established the cut-off values based on the minimum-maximum values in the normal BM in each age group. The expression of CD10 was higher than the cut-off in 30 ALL cases and in 18 of them there was a concomitant aberrant expression of other markers, In 9 of the 10 CD1 0(+) ALL with normal CD10 SABC values, the expression of at least one other marker was aberrant. In conclusion, the distinction between normal and leu kemic cells by QFC was possible in 38/40 CD10(+) ALL cases.