TLR7 and infection: In order to determine whether this effect was specific for IAV, MDDCs were treated with agonists for the Toll-like receptors (TLR) 3, TLR4 and TLR7/8 (Poly I:C, LPS, R848 respectively) for either 4 h or 24 h prior to infection with SP (Fig. 3C and D).