Increases in the numbers of cells with the phenotype of myeloid-derived suppressor and regulatory T cells in children with acute lymphoblastic leukemia

Abstract

Abstract Background Acute lymphoblastic leukemia (ALL) is the most common cancer diagnosed in children. The precise mechanisms behind the relapse in this disease are not clearly known. One possible mechanism could be the accumulation of regulatory cells including myeloid-derived suppressor cells (MDSCs) and T regulatory cells (Tregs) which we and others have reported to mediate suppression of anti-tumor immune responses. Few previous studies investigated the roles of Treg cells in ALL, while no studies reported the emergence of MDSCs in ALL. Aim Therefore, we aimed to analyze the frequencies and phenotype of these cells in a group of Egyptian B-ALL pediatric patients (n=45). Materials and methods MDSCs were identified as Lin− HLA-DR− CD33+CD11b+; and Treg cells as CD4+CD25+CD127−/low using multiparametric flow cytometer. Results We found significant increases in the numbers of MDSCs and Treg cells in B-ALL patients as compared to healthy control volunteers. B-ALL patients showed significant increased numbers of MDSCs and Tregs before chemotherapy when compared to healthy volunteers. The numbers of MDSCs were more increased while the numbers of Treg cells were more decreased in patients during induction of chemotherapy. The highest increase in the numbers of MDSCs was observed in patients after induction of chemotherapy, while Treg cells showed the most significant decreased numbers after induction of chemotherapy. Conclusion Our results indicate that B-ALL patients harbor both MDSCs and Treg cells, opening a new avenue to investigate the mechanism mediating the emergence of these cells in larger numbers of patients at different treatment stages.