A critical role for direct TLR2-MyD88 signaling in the formation of memory CD8 T cells. A total of 10⁴ naive WT, MyD88^−/−, or TLR2^−/− clone 4 CD8 T cells (Thy1.1⁺) were transferred into WT (WT→WT, MyD88^−/− →WT, or TLR2^−/−→WT) or MyD88^−/− (WT→MyD88^−/−) recipient mice (Thy1.2⁺) that were infected with 5 × 10⁵ pfu rVV-HA intraperitoneally. (A) Splenocytes were harvested at days 0, 7, 14, 28, or 42 after infection to determine the absolute number of the CD8⁺Thy1.1⁺ population per spleen, shown with SDs indicated (n = 4 per group). (B) At 42 days after infection, splenocytes were stained with anti-CD8 and anti-Thy1.1. The percentages of clonotypic T cells among total lymphocytes (top) and IFN-γ–producing clonotypic T cells among total CD8⁺ T cells (bottom) are indicated. Data shown are representative of 3 independent experiments.