C3^−/− mice show greater weight loss and mortality during influenza infection.

<p>(<b>A</b>) Percentage of body weight loss after influenza infection. A weight loss of <20% and recovery represents a sub-lethal infection. (<b>B</b>) Survival curve comparing WT and C3^−/− mice during influenza infection (n = 6–7 in each group). (<b>C</b>) Plots represent <i>ex vivo</i> analysis of CFSE-labeled OT-I CD8⁺ T cell proliferation in the dLN 3 days after infection with PR8 and PR8-OT-I (bottom). The graph on the right shows the respective division index for the proliferating OT-I CD8⁺ T cells for each group of mice. (<b>D</b>) Plots represent <i>ex vivo</i> analysis of CFSE-labeled OT-II CD4⁺ T cell proliferation in the dLN 3 days after infection with PR8 and PR8-OT-II (bottom). The graph on the right shows the respective division index for the proliferating OT-II CD4⁺ T cells for each group of mice. (<b>E</b>) Histogram showing expression of costimulatory molecules CD86, CD80 and CD40 on CD103⁺ DCs and CD11b⁺ DCs in the dLN on day 2 post infection. Filled histogram: Isotype control, dashed histogram: Naïve, open histogram: infected. (<b>F</b>) Bar graphs show the mean fluorescent intensity (MFI) of CD86, CD80 and CD40 expression on CD103⁺DC and CD11b⁺ DC subsets in the dLN of naïve and influenza infected (Day 2) WT or C3^−/− mice. (<b>G</b>) Plots represent CFSE-labeled OT-I CD8⁺ T cell proliferation 3 days after co-culture with sorted CD103⁺ DCs and CD11b⁺ DCs obtained from pooled dLN of PR8-OT-I influenza infected mice at a ratio of 1∶10 (DC:T cells). Results shown are representative of four experiments with similar results. The values are expressed as mean ± SEM.