The Role of Neutrophils during Mild and Severe Influenza Virus Infections of Mice
Figure 6
Neutrophils play a beneficial role during severe influenza infections of mice.
(A) Groups of 5 B6 mice were treated with purified anti-Ly6G (1A8) or rat IgG (IgG) antibodies 24 hrs prior to virus infection and every second day thereafter. Data show weight loss for mice infected with 102 PFU of PR8. (B) Groups of 5 B6 or B6.RAG-2γc−/−mice were infected with 102 PFU of HKx31 and at day 5 and 9 post-infection, mice were killed and BAL performed. Numbers of BAL neutrophils from virus-infected mice are shown. Neutrophils were identified via differential counts and Diff Quick staining, as described in Material and Methods. * = neutrophil numbers from B6.RAG-2γc−/− mice were significantly higher compared to numbers from B6 mice (p<0.01, one-way ANOVA). (C) Immunocompetent B6 mice (upper panels) or B6.RAG-2γc−/−mice (lower panels) were treated with purified anti-Ly6G antibodies (1A8) (i) at days −1, +1, +3, +5, +7, +9 and +11 (Continuous treatment, left panels), or (ii) at days +5, +7, +9 and +11 (Late treatment, right panels) relative to infection with 102 PFU of HKx31 at day 0. Control mice received a similar treatment regime of rat IgG (IgG). Arrows indicate the days mice were treated with mAb 1A8 or control rat IgG. Mice were weighed daily and results expressed as the mean percent weight change of each group (± SEM), compared to original body weight. Animals that had lost ≥25% of their original body weight and/or presented with evidence of pneumonia were euthanized. Data shown are from one experiment and are representative of two independent experiments. Dashed lines indicate days on which the weight loss induced by treatment with (A/C) mAb 1A8 was statistically different to IgG-treated controls (p<0.05, Student's t-test).