Endogenous pyrogens
- The endogenous pyrogens are cytokines that induce fever and include interleukin-1 (IL-1), IL-6, IL-8, macrophage-inflammatory protein-1 (MIP-1), and interferon-g (IFN-g )
- Polypeptides produced by a variety of hosperdero cells such as monocytes or macrophages, neoplastic cells that explain the existence of fever in malignancies.
The endogenous pyrogens converge to a brain region that regulates the fever, the preoptic area (POA) of the anterior hypothalamus. Mechanism controversy as endogenous pyrogens have to cross the blood brain barrier (BBB) which is impermeable to them. At least two routes are evident : Active transport across the BBB by carrier-specific cytokines.
Message transfer where the BBB has fenestrations, ie sensory organs circumventriculares particularly in the organum vasculosum laminae terminalis (OVLT). But there are alternative routes: the circulation of cytokines induce the generation of prostaglandin E2 (PGE-2) and perhaps prostaglandins F2a (PGF-2a) permeable to the BBB, the most proximal putative mediator of fever, endothelial cells the cerebral microvasculature or perivascular macrophages and microglia and meningeal. Direct transmission to the POA of pyrogens messages via peripheral afferent (mostly vagal) activated by cytokines.
