FIG. 1.

Lysis of IV-infected 1106mel cells by a primary human NK line. The cytotoxic activity was assessed in a 5-h ³⁵S release assay (15). 1106mel cells (10⁶) were infected overnight with 200 hemagglutination units/ml (600 hemagglutination units total) and labeled with ³⁵S. Following infection, all cells expressed membrane-associated HA as detected by antibodies to H1 or H5. NK cells were incubated with either uninfected 1106mel cells or VNH5N1-PR8/CDC-rg-infected (VNH5N1-PR8/CDC-rg-Inf.) or A/PR/8/34 (H1N1)-infected 1106mel cells at the indicated E:T ratios. Results are representative of three independent experiments performed with primary NK lines derived from different healthy donors. Bars, ± standard deviation (SD).