ALLOANTIGEN PRESENTING CAPACITY, T-CELL ALLOREACTIVITY AND NK FUNCTION OF G-CSF-MOBILIZED PERIPHERAL-BLOOD CELLS

In this study we addressed whether the proportion and the function of antigen presenting cells (APC), T and NK lymphocytes are modified in t he apheresis product of six healthy donors who received a stem cell mo bilizing treatment with glycosylated G-CSF at 10 mu g/kg/day x 5 days s.c. Flow cytometry analysis showed comparable percentages of HLA-DR+, CD19(+), CD86(+), CD80(+) and CD1a(+) cells in preG-CSF-peripheral bl ood mononuclear cells (preG-PBMC) and after mobilization in G-PBMC, wh ereas the proportion of CD14(+) monocytes significantly increased in G -PBMC (3 +/- 1% vs 17 +/- 8%, P = 0.003). Analysis of lymphocyte subse ts in preG-PBMC: and G-PBMC showed similar proportions of CD3(+), CD4( +), CD8(+) and CD28(+) T cells, but a significantly lower percentage o f CD16(+) (11 +/- 7% vs 4 +/- 1%, P=0.01), CD56(+) (15 +/- 6% vs 5 +/- 2%, P=0.008), CD57(+) (16 +/- 9% vs 5 +/- 2%, P=0.04), CD25(+) (19 +/ - 2% vs 9 +/- 6%, p=0.009) and CD122(+) (5 +/- 2% vs 2 +/- 1%, P = 0.0 5) cells in G-PBMC. Unfractionated preG-PBMC and G-PBMC were irradiate d and tested in primary mixed leukocyte culture (MLC) with two HLA-inc ompatible responders and induced efficient alloresponses in four of si x cases, whereas G-PBMC stimulated poorly in the remaining two cases. Also, in allo-MLC with irradiated G-PBMC we detected lower amounts of IFN-gamma (P=0.04) and of IL-2 (P=0.06) than in allo-MLC with preG-PBM C. Furthermore, freshly isolated preG-PBMC and G-PBMC from each donor exerted comparable allogeneic responses to HLA-incompatible irradiated mononuclear cells in all cases. However, G-PBMC showed no NK activity against K562 target cells at any effector:target ratio tested. These data suggest that normal G-PBMC may prevent Th1 alloresponses, maintai n efficient alloreactivity to HLA mismatched antigens and have impaire d NK activity.