Indispensable role of nasal NK cells in influenza virus infection.

<p>a. Change of nasal NK cells after infection with PR8 1×10³ pfu/mouse intranasally. Horizontal axis, day after infection; vertical axis, percentage of nasal NK cells in CD45⁺ lymphocytes (left) or absolute count of nasal NK cells (right). *, <i>P</i> < 0.05 **, <i>P</i> < 0.01 (Mann-Whitney <i>U</i> test with Ryan’s multiple comparison method). Data are obtained from at least 3 independent experiments. b. CD69 expression of nasal NK cells after intranasal infection with influenza virus PR8 (1×10³ pfu/mouse). Histogram (left). Dashed line, naïve; solid line, day 2 after infection; bold line, day 5 after infection. Dot plot of MFI (right). Data are representative of 2 independent experiments with 4 mice. c. Nasal virus titer of mice intranasally infected with influenza virus PR8 (1×10³ pfu/mouse). Mice were injected intraperitoneally with 100 mg PK136 antibody or an isotype-matched control on days –2, 0, 2 after infection. Bar, mean; horizontal axis, day after infection; vertical axis, virus titer (pfu). Data are representative of 3 independent experiments with 4 to 6 mice in each group. n.s., not significant; *, <i>P</i> < 0.05 **, <i>P</i> < 0.01 (Mann-Whitney <i>U</i> test with Ryan’s multiple comparison method). Data are obtained from at least 3 independent experiments.