TLR4 and pemphigus foliaceus: In TLR4 knockout mice, PF has been shown to be significantly attenuated by inhibiting fibroblast activation and collagen production, while the upregulation of fibroblast TLR4 augments transforming growth factor-beta 1 (TGF-β1) sensitivity in bleomycin- (BLM-) induced PF [11].