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

(A) 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-F) 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) and frequency of GP33 tetramer-specific CD8⁺ T cells and their PD–1 expression among CD8⁺ T cells (C) 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 (D). (E) Lymphocytes isolated from the spleen of mice at 31 DPI were restimulated in vitro 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. (F) 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-D) are data pooled from two independent experiments. Data of (E and F) are representative of four independent experiments (n≥3 per group in each experiment). NS, not significant.