Fig 3. Infection of human lung macrophages by X31.

Human lung macrophages were isolated by plate adherence prior to infection with 4000 pfu/ml of H3N2 X31 influenza virus or a UV-irradiated aliquot of virus (UVX31) for 2 h. After washing, media was replaced and the cells incubated for a further 22 h before supernatants and cells were harvested. Cells were analysed for intracellular viral NP1 expression or cell surface expression of HLA-DR and PD-L1 using flow cytometry. Histograms showing flow cytometry data of A) Viral NP1 expression (% cells), B) HLA-DR expression (specific mean fluorescence intensity—SMFI) and C) PDL1 expression (SMFI) from isolated human lung macrophages are expressed as means ±SE of 4 independent experiments. D) Representative histograms demonstrating increase in PDL1 expression in response to influenza infection are shown. Data analysed using a paired t-test * p<0.05, ** p<0.01.