FIG. 7.

Influenza virus HA inhibits Syk and ERK phosphorylation induced by target cell stimulation. Primary NK cells were treated with 1 μg/ml HA or left untreated (Mock) for 24 h. The cells were collected and cocultured with (stimulation) or without (resting) K562 cells at a ratio of 1:1 for 5 min. NK cells then were examined by flow cytometry for the expression of intracellular phospho-Syk (A and C) or phospho-ERK (B and D). The increase in the percentage of phosphokinase expression in stimulated NK cells relative to that of resting cells was calculated. Flow figures are representatives of samples from four independent experiments. The data shown are means ± SEM from four different donors. *, P < 0.05; **, P < 0.01.