Local accumulation of eosinophils in young and aged mice. Vaccinated young and aged BALB/c mice were challenged with 106 PFU RSV A2 at day 28. (A) Lungs were harvested 4 days post-challenge, stained with H&E, and eosinophil infiltration was scored. Representative sections are shown. Arrows indicate eosinophils. (B) The boxed inset in Figure4A shows eosinophils (arrows) at higher magnification. (C) Eosinophil score ± SEM. Each symbol represents one mouse. (Brackets, P < 0.05, ANOVA).