CD8⁺ T cells responses in IL-4-deficient CIITA^Tg and control mice during LCMV clone 13 infection.

<p><b>(A)</b> Cells were isolated from the thymus of CIITA^Tg and IL-4^KOCIITA^Tg mice and expression of CXCR3 and CD44 on CD8 single positive (CD8SP) thymocytes were analyzed by flow cytometry. Numbers in the plots indicate the percentages of cells in each quadrant. (<b>B-F</b>) IL-4^KO and IL-4^KOCIITA^Tg mice were infected with 5 x 10⁵ PFU of LCMV CL–13 per mouse. PBMCs were collected at the indicated DPI for analysis. The numbers of GP33 tetramer-positive CD8⁺ T cells per 10⁶ PBMCs (<b>B</b>) and frequency of GP33 tetramer-specific CD8⁺ T cells and their PD–1 expression among CD8⁺ T cells (<b>C</b>) were assessed during the course of LCMV CL–13 infection by flow cytometry. Numbers in the plots indicate percentage of PD–1⁺ or PD–1^- GP33 tetramer-positive cells among CD8⁺ T cells. PD–1 expression level on GP33 tetramer-positive CD8⁺ T cells in PBMCs represented by MFI value (<b>D</b>). (<b>E</b>) Lymphocytes isolated from the spleen of mice at 31 DPI were restimulated <i>in vitro</i> with GP33, GP276, or LCMV peptide pool for CD8⁺ T cells. Frequency of IFN-γ- and TNF-α-producing CD8⁺ T cells were analyzed by flow cytometry. (<b>F</b>) Serum viral titer in IL-4^KO and IL-4^KOCIITA^Tg mice at the indicated DPI. Dashed line indicates the virus detection limit. Line graph shows mean ± SD. Data of (<b>B-D</b>) are data pooled from two independent experiments. Data of (<b>E and F</b>) are representative of four independent experiments (n≥3 per group in each experiment). NS, not significant.