Distribution of antigenic aberration in the bone marrow of acute leukemia in complete remission

Background : The aberrant, leukemia-associated antigen expression patterns allow us to discriminate leukemic blasts from normal precursor cells. Our major goal was to determine a guideline for the detection of minimal residual disease using CD20+/CD34+ and myeloid Ag+/CD19+ combination in the bone marrow of acute leukemia in complete remission (CR) after chemotherapy. Methods : Bone marrow samples from 117 patients with acute leukemia in complete remission after chemotherapy and from 22 healthy controls were immunophenotyped by triple staining and measured by flow cytometry. Results : The CD20+/CD34+ cells in the large lymphocyte gate (R1) ranged from 0% to 3.24% (0.8±0.82%, P=0.000) in CD20+/CD34+ B-lineage ALL CR (N=31), from 0.03% to 4.2% (0.7±0.83 %, P=0.000) in CD20-/CD34- B-lineage ALL CR (N=66), from 0.1% to 0.96% (0.45±0.32%, P=0.016) in T-ALL CR (N=10), and from 0.02% to 0.48% (0.18±0.15%, P=0.776) in AML CR (N=10). The CD13,33+/CD19+ cells in R1 gate ranged from 0% to 2.69% (0.37±0.48%, P<0.001) in CD13,33+/ CD19+ B-lineage ALL CR (N=31), from 0% to 1.8% (0.31±0.28%, P<0.001) in CD13,33-/CD19+ B-lineage ALL CR (N=65), from 0.02% to 0.64% (0.29±0.22%, P=0.071) in T-ALL CR (N=9), and from 0% to 0.17% (0.07±0.09%, P=0.341) in AML CR (N=3). Conclusions : Using an immunophenotypic method for the detection of early relapse or minimal residual disease of B-lineage ALL bone marrow in CR after chemotherapy, different cutoff values should be applied according to antigen combination and gating. When the proportion of aberrant antigen combination was less than 5% in large lymphocyte gate, the results should be interpreted with caution.