Figure 1. MIF increases in the airspace and enhances morbidity and mortality after infection with IAV.

MIF-knockout (Mif^–/–, white circles), WT (Mif^+/+, gray circles), and Mif-overexpressing Tg (Mif-lung-tg, pink circles) C57BL/6 background mice were challenged i.n. with 5 × 10⁴ PFU H1N1 PR8. (A) MIF in the BAL measured by ELISA. The mice were monitored daily for (B) survival, (C) body weight, and (D) clinical score. (E) Survival curve of WT mice injected i.p. with anti-MIF antibody (black squares) or mouse IgG (black circles) on days labeled with blue arrows and infected with 5 × 10⁴ PFU H1N1 PR8 at 0 DPI. Statistical differences were determined by (A) multiple t tests adjusted for multiple comparisons by Holm-Sidak test, (B and E) Gehan-Breslow-Wilcoxon test, or (C and D) 2-way ANOVA followed by Tukey multiple comparisons test. The violin plots are closed curves representing data distribution and encapsulate the median, range, and interquartile range, with each symbol representing a biological replicate (A). The data are displayed as mean ± SEM (C and D). There was no significant difference in survival rate between WT control groups in survival studies for Mif^–/– or Mif-lung-tg mice; a representative group is shown in B–D for clarity. Data are representative of 2 independent experiments, with n = 4–5/group (A), 15–18 mice/group at time of infection (B–D), or (E) 8–10 mice/group at time of first injection. For only C and D, significance is denoted between Mif^+/+ and Mif-lung-tg with a red asterisk; whereas, significant differences between Mif^–/– and Mif^+/+ were denoted with a black asterisk. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.