Autonomous NK commitment of PB-HP: morphology and expression of cytolytic granules.

<p>(A) Ral 555 staining on 3-weeks-old PB-HP cultured in in STEMα Α medium supplemented with 100 ng/ml of FL and SCF. PB-NKP exhibit a lymphoid morphology. (B) Intracytoplasmic expression of perforin and granzyme B in PB-NKP and in PB activated conventional NK cells was analyzed by confocal microscopy. Both cell types were fixed, permeabilized, and stained for perforin and granzyme B. As negative controls, cells were incubated with mouse IgG, and the second reagent. (C) Analysis of the cytolytic activity of freshly purified NK cells from healthy donors (open boxes) and from PB-NKP (grey boxes) against ⁵¹Cr-labelled K562 cells. NK cell effectors, treated or not for 18 hours with IL-12 (5 ng/ml), were assayed in a 4-h ⁵¹Cr-release assay against K562 cells in a dilution of E/T cell ratios (10∶1) in duplicate wells. Data are representative of three experiments performed.