Lysis of ES and <i>in vitro</i> differentiated cells by NK cells derived from naïve LOU/c rats and expression analysis of MHC class I molecules and NKG2D ligands.

<p>(A) Mean of specific lysis and standard deviation (SD) of triplicates of ES or <i>in vitro</i> differentiated cells at three effector∶target (E∶T) ratios. Effector cells were lymphocytes obtained from spleens of 10 individual LOU/c rats by density gradient centrifugation on Biocoll. Results obtained with lymphocytes from female rats are indicated by open symbols and from male rats by filled symbols. (B) The mean specific lysis and SD of triplicates of ES, YAC-1, and RMA target cells at three effector∶target (E∶T) ratios by freshly isolated NK cells or NK cell-depleted splenocytes from naïve LOU/c rats are shown. The NK cell enriched fraction contained 86% and the NK cell depleted fraction 3% NKR-P1A-positive cells as determined by flow cytometry. The results are representative for 3 independent experiments. (C) The mean specific lysis and SD of triplicates of ES and YAC-1 cells at three effector∶target (E∶T) ratios by freshly isolated (open symbols) or 3 days <i>in vitro</i> with 1000 U/ml IL-2 stimulated (closed symbols) mouse and rat NK cells are shown. The NK cell-enriched fractions contained more than 80% NK cells as determined by flow cytometry. The results shown are representative for 3 independent experiments. (D) The expression of MHC class I molecules on ES and differentiated cells was analyzed by flow cytometry using anti-H2K^b and anti-H2D^b Abs (full lines). The stainings with the isotype control are shown by the dotted lines. RMA cells (H2^b) served as positive control for these antibodies. NKG2D ligands were stained with a recombinant mouse NKG2D-Fc chimeric protein and a FITC-conjugated goat anti-human IgG antibody as secondary reagent (full lines). Stainings with the secondary reagent only are shown by the dotted lines. YAC-1 cells (H2^a) served as positive controls for these stainings. The results shown are representative for more than 3 independent experiments. (E) ES and as positive control YAC-1 cells were stained with the NKG2D-Fc chimeric protein and with mAbs specific for the NKG2D ligands H60, MULT-1, and RAE-1. The mean+SD of the proportion of positive cells and the mean fluorescence intensity+SD determined in 6 independent experiments is shown. (F) The mean inhibition+SD of specific lysis of ES and YAC-1 cells by soluble mouse NKG2D is shown as determined in 3 experiments. The mean of specific lysis of the target cells by rat NK cells at an effector to target ratio of 20∶1 was determined as described above and adjusted to 100%. For inhibition of lysis a soluble mouse NKG2D protein was added to the test at a concentration of 3 µg/ml. The relative lysis of the target cells exposed to NKG2D was calculated. (G) The mean inhibition+SD of specific lysis of ES cells by soluble mouse NKG2D and various inhibitory antibodies against NKG2D ligands is shown. The mean of specific lysis of the target cells by IL-2 activated mouse NK cells at an effector to target ratio of 10∶1 was determined as described above and adjusted to 100%. For inhibition of lysis a soluble mouse NKG2D protein or the indicated mAbs were added to the test at a concentration of 3 µg/ml. The relative lysis of the target cells exposed to NKG2D or the mAbs was calculated.