Characterization of peripheral blood stem cell grafts mobilized by granulocyte colony-stimulating factor and plerixafor compared with granulocyte colony-stimulating factor alone

Background aims. This study aimed to characterize the immune effectors contained in apheresis samples obtained from patients with grafts mobilized with plerixafor and granulocyte colony-stimulating factor (G-CSF) (P+G) compared with grafts mobilized with G-CSF alone (G). Methods. Aliquots of apheresis samples were obtained from 36 patients with malignant diseases after mobilization with G (n = 18) or P+G (n = 18). The phenotype and cytokine secretion profile of T cell and dendritic cell subsets were characterized by multicolor cytometry including intracellular cytokine staining. Results. In grafts collected after mobilization with P+G, there was a significantly higher percentage of CD3(+) T cells compared with samples collected after mobilization with G alone. On a functional level, a significant increase of interferon-gamma and tumor necrosis factor-alpha secreting CD8(+) T cells was observed in the P+G group compared with the G group. CD4(+)Foxp3(+) regulatory T cells were similar in both groups but exhibited a lower expression of inducible costimulatory molecule and a significantly higher expression of CD 127 in the P+G group. Myeloid dendritic cells (MDCs) and BDCA3(+) dendritic cells were similar in both groups. In contrast, plasmacytoid dendritic cells (PDCs) (CD123(+)BDCA2(+)HLA-DR+) were significantly increased in the P+G grafts, leading to a higher PDC-to-MDC ratio. PDCs mobilized by P+G displayed different functional markers-a higher percentage of ILT7(+) PDCs and decreased expression of CD86-suggesting a potential regulatory capacity of PDCs mobilized by P+G. Conclusions. Grafts mobilized with P+G exhibited major different functional features compared with grafts mobilized with G alone, suggesting that such grafts may have an impact on patient outcome after autologous stem cell transplantation.