FIG. 5.

Analyses of NK cell functions. (A) Antibody-mediated cellular cytotoxicity. NK cells were incubated at the indicated ratios of effector cells to target cells with ⁵¹Cr-labeled EL-4 target cells, in the presence or absence of anti-Thy MAb G7 (which binds Thy1 on EL-4 and triggers CD16 on NK cells). Target cell lysis was determined by measuring ⁵¹Cr release in the supernatant (values are percentages of maximal release). Standard deviations are shown. (B) IFN-γ secretion. Cells were stimulated with the indicated antibodies (1 μg per ml), IL-12 (5 ng per ml), or PMA (50 ng per ml) plus ionomycin (1 μg per ml). After 24 h, the production of IFN-γ was measured in the supernatant by ELISA. Standard deviations are shown. Similar results were obtained over a range of different antibody concentrations (data not shown). Standard deviations are represented. (C) Natural cytotoxicity. NK cells were stimulated at the indicated ratios of effector cells to target cells with ⁵¹Cr-labeled RMA (MHC class I-positive) or RMA-S (MHC class I-negative) cells. After 4 h, natural killing was assessed by measuring the release of ⁵¹Cr in the medium. Values are presented as percentages of maximal release. Standard deviations are shown.