The reduced expression levels of TLR2, TLR4 and TLR9 mRNAs or proteins can enhance protection against T cell-mediated hepatitis in mice [22], and the reduced expressions of TLR4, MyD88 and NF-κB may mediate the protective effects against LPS through reducing the level of pro-inflammatory cytokines [23]. Here, MYD88 is linked to hepatitis A virus infection.