The recent Blood article by Schroeder et al. demonstrates that plerixafor mobilizes a
unique hematopoietic stem and progenitor cell (HSPC) product that is enriched in plasmacytoid
dendritic cell precursors (pre-pDCs).
This study further reports that enrichment of these cells in
plerixafor-mobilized allografts is associated with lower cumulative incidence of acute and
chronic graft-versus-host disease (GvHD). In an earlier study, Waller et al. reports a protective
advantage against acute GvHD (aGvHD) of pDCs derived from bone marrow but not
granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood (PB) graft.
Studies
have shown that allogeneic transplantation with bone marrow (BM) allograft results in lower rate
of acute and chronic GvHD when compared to G-CSF-mobilized PB graft. In his commentary to
the Schroeder study, Waller proposes that the relatively rapid onset of mobilization by plerixafor
(hours vs. days by G-CSF) generates a novel PB graft that immunologically and phenotypically
resembles cells harvested from bone marrow.3
He hypothesizes that this unique allograft
contains immune subsets, including pre-pDCs and pDCs, which favorably modulate
alloreactivity post-transplantation thus resulting in lower GvHD rates.
