Fig. 4.

fmOMV activates macrophages and induces antiviral cytokines in the lung tissue. a Mice were intranasally administered with 10 µg of Alexa Fluor 488 (Alexa488)-labeled fmOMV. After 3 h, the population of Alexa488 and F4/80-positive cells were determined by flow cytometry, gated on CD45⁺SiglecF^hiCD11b^loCD11c^hi bronchoalveolar lavage cells. b The expression of activation markers on macrophages (upper panels) and neutrophils (lower panels) in the lungs were analyzed at 3 days after fmOMV injection. c, d The levels of type I interferons, IL-1β, and C-C motif chemokine ligand 2 (CCL2) in the lungs were determined by RT-PCR and multiplex cytokine immunoassay, respectively. e Type I IFN receptor 1 knockout (IFNAR1KO) mice (n = 4 or 6) were injected with fmOMV. Three days after the injection, the mice were infected with PR8 virus, and the survival rates were monitored for 2 weeks after the viral challenge. Data are presented as mean ± SEM and representative of at least three independent experiments. *** p < 0.001, ** p < 0.01, * p < 0.05.