TLR4 and acute pyelonephritis: Previous studies in acute pyelonephritis have found that, paradoxically, Tlr4-/-, Il1b-/-, or C3-/- mice or mice receiving anti-inflammatory mediator cyclic AMP had less severe acute kidney infection and inflammation, suggesting that innate immune responses driven by TLR4 signaling, pro-inflammatory cytokine IL-1β, or complement effector molecules are harmful, rather than beneficial, for the host (Springall et al., 2001; Yadav et al., 2010; Wei et al., 2015).