No Polarization of Type 1 or Type 2 Precursor Dendritic Cells in Peripheral Blood Stem Cell Collections of Non-Hodgkin's Lymphoma Patients Mobilized with Cyclophosphamide Plus G-CSF,GM-CSF,or GM-CSF Followed by G-CSF

Abstract

Dendritic cells (DCs) are the most efficient antigen-presenting cells and play a role in immune reconstitution after autologous transplantation. Recent reports suggest that mobilization with granulocyte colony-stimulating factor (G-CSF) containing regimens polarizes DCs into pDC2, which could potentially result with increased Th2 response and decreased graft-versus-host disease (GVHD) in allogeneic transplantation and with decreased cytotoxic Th1 response and graft versus tumor effect, which in autologous transplantation could translate into increased relapse rate. Previously, we have shown that non-Hodgkin's lymphoma (NHL) patients receiving cyclophosphamide (CTX) plus granulocyte- macrophage (GM)-CSF, G-CSF or GM-CSF followed by G-CSF for stem cell collection, mobilize up to five-fold more mature CD80⁺ DCs compared to CTX plus G-CSF mobilized patients. Here, we analyzed samples from the same study for the number of pDC1 and pDC2 subsets in blood and apheresis products obtained from these patients. Samples from 29 patients were collected. Patients mobilized with CTX plus G-CSF collected a mean of 1.2 ± 0.4 × 10⁶ pDC1/kg per day and 2.2 ± 1 × 10⁶ pDC2/kg per day, whereas patients mobilized with CTX plus GM-CSF collected a mean of 1.1 ± 0.5 × 10⁶ pDC1 and 1.5 ± 0.9 × 10⁶ pDC2/kg per day. Patients mobilized with CTX plus GM-CSF followed by G-CSF collected 2.5 ± 1.1 × 10⁶ pDC1 and 2 ± 0.5 × 106 pDC2/kg per day, with significantly higher levels of pDC1 ± pDC2 cells. No significant difference was observed in pDC1/pDC2 ratio between the three mobilization arms. Patients mobilized with the GM-CSFcontaining regimen had a higher probability for survival compared to patients receiving G-CSF alone (median of 55 months vs. 15 months; p = 0.02). These results support the hypothesis that higher levels of DCs in the graft might be associated with prolonged survival of autotransplanted NHL patients. Further similar studies are merited in a larger population of NHL patients.