[Flow cytometric detection of minimal residual disease in pre-cursor-B-acute lymphoblastic leukemia on the basis of phenotypic aberrancies on minor leukemic cell populations].

To test the European BIOMED-1 Concerted Action proposed technique to detect minimal residual disease (MRD) in the chinese patients with precursor-B-acute lymphoblastic leukemia (precursor-B-ALL) by triple-staining flow cytometry and to define both normal and aberrant phenotypic profiles of precursor B cells, a series of bone marrow samples, 35 from precursor-B-ALL (13 in newly diagnosed cases, 15 at the end of remission induction therapy and 7 at end of the consolidations), and 19 from normal controls, were immunophenotyped with the five triple-staining antibodies (TdT/CD10/CD19, CD10/CD20/CD19, CD34/CD38/CD19, CD34/CD22/CD19 and CD19/CD34/CD45) recom-mended by the BIOMED-1 using common flow cytometric protocols. Further, with different ratios of the leukemic cells with CD34/CD38/CD19 phenotype and normal mononuclear cells, a serial dilution test was analyzed. The results showed that three major CD19(+) cell subpopulations were identified in the normal controls, representing three consecutive maturation stages. The subpopulations in the precursor-B-ALL cases disappeared and were replaced with a great number of luekemic cells which had different characteristics of phenotypes, and then they reappeared with almost same characteristics as the normal CD19(+) cells after the patients achieved complete remission. When the five triple-staining antibody combinations were used, the phenotypic aberrancies could be identified in 12/13 (92.3%) cases with newly diagnosed precursor-B-ALL, at least one triple-labeling per case at the level of 0.01% or more. The frequencies of phenotypic aberrations detected with the triple-staining were 8/13 (61.5%) for CD10/CD20/CD19, 5/13 (38.5%) for CD34/CD38/CD19, 4/13 (30.8%) for CD10/TdT/CD19, 3/13 (23.1%) for CD34/CD22/CD19, and 2/13 (15.4%) for CD34/CD45/CD19. At the end of remission induction, the phenotypic aberrancies could be detected in 5/15 (33.3%), of which, 3/8 (37.5%) cases with the leukemic phenotypes detected both at the newly diagnosis and at the end of induction. The dilution test indicated that the cells with CD34/CD38/CD19 detected by flow cytometry correlated well with the leukemic cells added (r = 0.85, P < 0.05) over 1:1 to 1:400,000. It is concluded that the flow cytometric detection of precursor-B-ALL-MRD proposed by BIOMED-1 Concerted Action were well realized in this study. The one precursor-B-ALL cell can be effectively detected out of 10(4) normal bone marrow cells.