Figure 3.

Cytokine detection of T cell-specific immune response in serum at day 6 p.i. and presence of cytotoxic T cell activity. Mice were infected with either a low or high dose of IAV and T cell specific cytokines were detected in serum 6 days p.i. The levels of (A) IFN-γ, (B) IL-4, (D) IL-10, and (E) TNF were measured using the Bio-plex 200 system and compared to uninfected control mice. The groups consisted of three mice each. The samples were measured twice independently. (C) The ratio of IFN-γ/IL-4 is used to determine the Th1/Th2 profile. A ratio above 1 means there is a predominance for Th1 response, and a ratio between 0 and 1 stands for a Th2 immune response. (F) Influenza A virus specific CD8⁺ T cells in the lungs 6 days p.i. with low dose (blue bar) or high dose (red bar) analyzed by flow cytometry. Percentage was determined by fluorescent pentamers in the CD8⁺ T cells. Values shown as mean ± SD (n = 3) (G) In vitro cytotoxicity assay using IAV specific CD8⁺ lymphocytes from the lungs of mice infected with either low dose (blue squares) or high dose of IAV (red circles). Target cells were labeled with ⁵¹Cr and loaded with the immunodominant influenza peptide NP_366-374. The NP specificity of the CD8⁺ T cells were determined by the ⁵¹Cr release of lysed target cells. Values reflect the mean of two measurements from a cell pool of two animals each.