CD69 and infection: Similar to MHC II, CD69 expression on NK cells from WT mice also increased significantly after infection (8.34 ± 2.18% versus 15.39 ± 0.69%, P < 0.05, Figure 1(d)), and there was no difference between infected and noninfected TLR3 KO mice (11.10 ± 2.04% versus 10.66 ± 3.37%, P > 0.05, Figure 1(d)).