Fig. 1

Adiponectin exacerbates influenza infection in old age via IL-18. a Adiponectin concentration in human BALF samples obtained from young (18–35) or old (60–74) patients with or without influenza (n = 8–13). b Gene and (c) Protein expression of adiponectin from cultured lung samples obtained from young (18–35 old) or old (60–74 old) patients with or without influenza. d Gene expression of cytokines from lung biopsies obtained from young (18–35 old) or old (60–74 old) patients with or without influenza (n = 8). e IL-18 mRNA expression in cultured lung samples obtained from young (18–35 old) or old (60–74 old) patients with or without influenza treated with either the vehicle control (H₂O) or human rAdiponectin (3 μg/ml) for 24 h (n = 3). f H&E staining of the lungs (g) survival rate of influenza-infected (10×MLD₅₀ H1N1 influenza virus) WT or Adipoq^−/− young (3 months to 9 months old) and old (20 months to 24 months old) mice (n = 6–12). h H&E staining of the lungs (i) survival rate of influenza-infected (10×MLD₅₀ H1N1 influenza virus) WT young (3 months to 9 months old) and old (20 months to 24 months old) mice treated with either the control (IgG1: 50 µg per mouse daily) or with mouse adiponectin antibody (50 µg per mouse daily) until the final timepoints (n = 6–12). All RT-qPCR gene expression levels were normalized to the endogenous level of 18 s. All data are expressed as the mean ± S.E.M. of n observations. A Student’s unpaired t test or ANOVA with Tukey’s comparison were used for statistical analysis. Survival curves were compared using log rank Mantel–Cox curve comparison, and groups were compared to either old Adipoq^−/− mice or old WT mice + rAdiponectin in their respective graphs. NS = non–significant. p < 0.05, p < 0.01, p < 0.001 or p < 0.0001 are represented in figures as *, **, *** or ****, respectively