TNF and infection: Nociceptors are also modulated by the immune cells of the innate and acquired immune systems under pathological conditions resulting from tissue injury and infection by responding to molecular modulators including cytokines (tumor necrosis factors [TNF], interleukins (IL), interferons [IFN], chemokines [e.g., CCL1, CCL2], transforming growth factor [TGF], and prostaglandins (e.g., PGE2) [37].