Figure 1.

Sorted neutrophil progenitor cells from bone marrow do not exert MDSC activity. Neutrophil progenitors from bone marrow were isolated via FACS sorting based on CD11b and CD16 expression under cold conditions and with a small nozzle. (A) Purified CFSE-labeled T cells from healthy donors (n = 6) were cultured with anti-CD3 and anti-CD28 antibodies (white bars), and in presence of mature neutrophils from control donors (black bars, n = 6) or sorted neutrophil progenitors from bone marrow (gray bars, n = 3) and/or indicated stimuli. Cells were harvested after 5–6 days and analyzed by flow cytometry for CFSE dilution among CD4⁺ T cells. (B) The surface marker expression of FPR-1 and fMLF binding (top panel, n = 3–8), TNF receptor I and II (center panel, n = 4) and TLR4 (bottom panel, n = 4) was measured by flow cytometry analysis of mature neutrophils from blood (black bar) and neutrophil progenitors from bone marrow. (C) Mature neutrophils and neutrophil progenitors were stimulated with the indicated stimuli and production of H₂O₂ was determined by measuring Amplex Red conversion into fluorescent Resorufin (n = 3). Error bars indicate SEM; ^****p < 0.0001.