TLR4 and influenza: As previously reported in C57BL/6J versus TLR4-/- mice (20, 24), the TLR4 signaling-deficient C3H/HeJ strain was significantly more resistant to PR8-induced lethality than the closely related, LPS-responsive C3H/OuJ strain from which it was derived when challenged with either a sublethal (p = 0.0118) or lethal dose (p = 0.0004) of influenza strain PR8.