TNF and infection: Keratinocytes are well equipped for pathogen sensing as they express a broad spectrum of pattern recognition receptors (PRRs), including surface and endosomal toll-like receptors (TLRs), NOD-like receptors (NLRs), and retinoic acid-inducible gene (RIG-I)-like receptors, and rapidly respond to cell injury and infection by releasing critical pro-inflammatory chemokines and cytokines such as tumor necrosis factor α (TNFα) and interleukin 1 (IL-1) [7,8].