noun, plural: pyrogens
Pyrogens are substances that induce fever. They act on the hypothalamic thermoregulatory center. They inhibit the heat-sensing neurons while stimulating the cold-sensing neurons, thus, resulting in the hypothalamus increasing body temperature above the normal range. The result is a condition called fever. The action of pyrogen resulting in a febrile response is thought to be a part of the body's ability to combat infection. The increase in body temperature may kill or inhibit the growth of infectious microbes that cannot tolerate a higher temperature range. The rise in body temperature may also help stimulate motion, activity, and multiplication of white blood cells as well as increase the production of antibodies.1
There are two types of natural pyrogens: (1) endogenous pyrogens that the host's pyrogen cytokines and (2) exogenous pyrogens that are microbial substance (e.g. lipopolysaccharides in the cell wall of certain bacteria).
Word origin: Latin pyr, from Ancient Greek pûr (fire) + Ancient Greek –genḗs (producer of) Synonym(s):
1 The Editors of Encyclopædia Britannica. 2014. Fever. Britannica.com. Retrieved from http://www.britannica.com/EBchecked/topic/205674/fever