FIG 3.

Immunization of CD47KO induces enhanced protection against influenza virus infection. Immunized WT and CD47KO mice were challenged with a lethal dose of A/PR8 influenza virus (8 × LD₅₀ [A and B] or 33 × LD₅₀ [C and D]) at 6 weeks after boost immunization. Body weight changes (A and C) and survival rates (B and D) were monitored daily for 14 days. (E and F) Viral titers in BALF (E) and lungs (F). Mice were infected with A/PR8/34 (8 × LD₅₀), and the lung tissues were harvested at 6 days postchallenge. The viral titers were determined by inoculating chicken eggs with diluted lung samples. EID₅₀, 50% egg infectious dose. “Naive” indicates unimmunized WT mice. The statistical significance was determined by using an unpaired two-tailed Student t test or one-way ANOVA. Error bars indicate the means ± the SEM of the concentrations or ratios from individual animals. *, P < 0.05; **, P < 0.01; ***, P < 0.001.