Immunological properties of mononuclear cells from blood stem cell harvests following mobilization with erythropoietin + G-CSF in cancer patients

Background: Although the recombinant granulocyte colony-stimulating factor (G-CSF) is a good CD34 cell mobilizer, the effects of G-CSF mobilization on the immune effector function of the individual is not always optimal. We studied the functional and phenotypic properties of peripheral blood stem cells (PBSC) collected from 15 cancer patients mobilized with G-CSF plus recombinant erythropoietin (EPO). Methods: The patients received EPO (300 U/kg) and (G-CSF 10 μg/kg) per day as mobilizing cytokines and an autologous graft product was collected with at least daily apheresis procedures until a target number of CD34 cells and mononuclear cells were obtained. Mononuclear cells from the first four PBSC collections were tested for their natural killer (NK), activated NK and lymphokine activated killer (LAK) cytotoxicity in vitro against K562 and Raji tumor target cells. Results: There was a significant increase in NK, activated NK and LAK cytotoxicity in EPO + G-CSF mobilized cells when compared to mononuclear cells from premobilization blood baseline values. Although there was no increase in CD3⁺ T cells, there was a significant increase in myeloid cells (CD14⁺), B-cells (CD20⁺) and NK cells (CD56⁺) following mobilization. There was no difference in T cell response to the mitogens PHA and Con-A, but there was an increase in B-cell response to PWM following mobilization. Thus, the combination of EPO + G-CSF not only mobilized hematopoietic precursor cells but also increased the number of immune effector cells in the PBSC collections.