<prompt> Fever occurs due to -IL 1EndoephinEnkephalinHistamine  <response>: Ans. is a i.e., IL1 Pyrogeneso Pyrogenes are substances that cause fever.o Pyrogens may be exogenous or endogenous Exogenous- Bacterial toxins Endogenous- IL0-l,TNF-a, IL-6, Interferons, Cilioiys neurotropic factoro These pyrogenes increase the level of PGE2 in the hypothalamus that elevates the thermoregulatory set point and causes fever. 