Morbidity, inflammation, and neutrophil number are increased after infection with high dose influenza virus.

<p>(A) Kinetics of weight loss as a percentage of starting weight in C57BL/6 mice infected i.n. with 125 (<i>light-grey squares</i>), 1250 (<i>dark-grey triangles</i>), or 12500 (<i>black circles</i>) EID₅₀ PR8 virus. Mean ± SEM (n = 5, representative of four independent experiments). (B) Cytokine and chemokine levels in the BAL of uninfected mice (‘control’, <i>clear bars</i>) or mice infected 6 days earlier with 125 (<i>light-grey bars</i>), 1250 (<i>grey bars</i>), or 12500 (<i>dark-grey bars</i>) EID₅₀ PR8 virus. Mean ± SEM (n = 3–4, representative of two independent experiments). (C) Histological examination of uninfected lungs (control, <i>left</i>) or lungs 6 days after infection with 125 (<i>middle</i>) or 12500 (<i>right</i>) EID₅₀ PR8 virus. Perfused lungs were fixed in formalin and stained for hematoxylin and eosin (scalebar = 100 µm). Images are representative of multiple mice. b. bronchiole, a. arteriole, av. alveole, and arrowhead. venule. (D) Neutrophil numbers in the BAL and lung of uninfected mice (‘control’, <i>clear bars</i>) or mice infected 6 days earlier with 125 (<i>light-grey bars</i>) or 12500 (<i>dark-grey bars</i>) EID₅₀ PR8 virus. Mean ± SEM (n = 3, representative of two independent experiments). (E) The percentage of blood neutrophils from LysM-GFP mice infected with 125 (<i>light-grey squares</i>) or 12500 (<i>black circles</i>) EID₅₀ PR8 virus compared to control (PBS, <i>open squares</i>) or allantoic fluid at the same dilution as the highest viral dose (<i>open triangles</i>). Mean ± SEM (n = 4–5).