Significance of CD34/CD123 expression in detection of minimal residual disease in B-ACUTE lymphoblastic leukemia in children.

BACKGROUND: MRD is seen as the major cause of disease relapse. So, it gives important feedback about conventional treatment success and helps in selecting therapeutic alternatives. We aimed to compare the expression of CD34/CD123 on normal B-cell precursors in bone marrow ("hematogones") and on leukemic blasts in B-acute lymphoblastic leukemias (B-ALL) pediatric cases by flowcytometric analysis. Our study conducted on 20 children as a control and 30 B-ALL children cases at diagnosis and after 28days of induction therapy. We found that the less mature hematogones (dim CD45+) that express CD34 lack CD123 expression, whereas the more mature hematogones (moderate CD45+) lack CD34 but always express CD123. In contrast with this discordant pattern of CD34 and CD123 expression in hematogones, blasts in 24 of 30 cases (80%) of B-ALL showed concordant expression pattern of the 2 antigens: 63% (19 of 30) cases expressed both antigens, whereas 17% (5 of 30) expressed neither. Our study concluded that these distinct patterns of CD34/CD123 expression on hematogones (discordant) and B-ALL blasts (concordant) are useful in differentiating small populations of residual blasts from hematogones after induction therapy to detect MRD.