Endogenous MyD88^−/− and TLR2^−/− CD8 T cells exhibit defective virus-specific effector response to VV infection in vivo. A total of 10⁶ purified WT, MyD88^−/−, or TLR2^−/− polyclonal CD8 T cells were transferred along with 2 × 10⁶ WT polyclonal CD4 T cells into RAG-2^−/− hosts. Seven days after transfer, mice were infected intraperitoneally with 5 × 10⁶ pfu VV or left uninfected (naive) as control. Seven days after infection, splenocytes were stained with anti-CD4 and anti-CD8 antibodies and subjected to intracellular staining with an anti–IFN-γ antibody after a 6-hours stimulation with the VV-specific peptide F2L (²⁶SPYAAGYDL³⁴). (A) The percentage of IFN-γ⁺ CD8⁺ T cells among total splenocytes for each respective population is indicated. (B) The absolute cell number per spleen of IFN-γ⁺CD8⁺ T cells for both naive and infected groups are shown with SDs indicated (n = 6 per group). For all groups: naive versus VV, P < .001. For VV-infected hosts: MyD88^−/− or TLR2^−/− versus WT, P < .001. Data shown are representative of 3 independent experiments.