Reduction in the numbers of CD33+ myeloid population in Egyptian children with B-linage acute lymphoblastic leukemia and its recovery after induction of chemotherapy

Background: Acute lymphoblastic leukemia (ALL) is biologically and clinically considered as a heterogeneous neoplasm of lymphoid progenitor cells. About 85% of children with ALL are diagnosed as B-ALL, expressing CD19; the typical marker of normal B cells. Problem: Given that the chemotherapy associated with leucopenia, in particular myeloid cells (CD33⁺ cells), Aim: the main aim of this study was to analyze the numbers of these cells in children with B-ALL before and after induction of chemotherapy. Materials and Methods: The frequencies of CD33⁺ myeloid cells and CD19+ B-cells were analyzed in the peripheral blood patients before (n = 10) and after (n = 10) induction of chemotherapy as well as in healthy volunteers (n = 10) using multiparametric flow cytometry. Results: As expected, B-ALL patients showed high numbers of CD19⁺ cells before induction of chemotherapy; where the numbers of these cells were reduced upon the induction of chemotherapy. CD33⁺ myeloid cells showed decrease in numbers in B-ALL patients before chemotherapy as compared to healthy control volunteers. Interestingly, treatment of B-ALL patients with chemotherapy-induced almost recovery of the numbers of these cells. Conclusion: CD33⁺ myeloid cells are increased in numbers after induction of chemotherapy, indicating to a dynamic mobilization or differentiation of their precursors into circulation. This study opens a new avenue to characterize the phenotype and function of these cells in different hematological malignancies; in particular, they may harbor regulatory cells.