Human NK Cells Differ More in Their KIR2DL1-Dependent Thresholds for HLA-Cw6-Mediated Inhibition than in Their Maximal Killing Capacity
A) Induction of CD107a and IFN-γ are not correlated. NK cells were co-incubated with (bottom) or without (top) 221 target cells and analysed by flow cytometry. NK cells were selected on the basis of size (left; FSC-H stands for Forward Scatter and correlates with the cell volume while SSC-H stands for Side Scatter and correlates with the granularity of the cell; NK cells are the smaller cells, while the larger events correspond to target cells) and analysed for CD107a degranulation and IFN-γ intracellular staining (right). B) Top: Amount of IFN-γ, determined by ELISA, secreted by different NK cell clones incubated for 72 hr with 100 U/ml IL-2, or in the presence of irradiated target cells (221 cells expressing no MHC class I, or target cell clones 6.2, 6.3, 6.4 or 6.6, expressing an increasing number of surface MHC class I molecules per cell – Table 1). Bottom: Percent of lysed target cells by NK cell clones as determined by 5 hr radioactive release assays (bottom), using the same target cell clones. C) CD107a degranulation (left) and IFN-γ production (right) by NK cells incubated with different target cells for different times. Data shown was obtained with an NK cell line, and are representative of data acquired with two NK clones and one polyclonal NK cell line. D) Correlation between inhibition of NK cell CD107a degranulation and IFN-γ production. NK cell clones were incubated with 221 cells or cells expressing different MHC-I levels for 5 hr and analyzed for CD107a degranulation and intracellular IFN-γ production (right, two clones are shown). Left: Pearson correlation coefficients between the percent of CD107a+ and that of IFN-γ+ NK cells upon co-incubation with target cells expressing different levels of MHC-I protein, calculated with SPSS v14 for Windows. Each circle represents one NK cell clone.