Saturday, November 6, 2010

Pyrogen


The substance that causes fever called pyrogens are derived either from exogenous or endogenous. Exogenous pyrogens originating from outside the host, while the endogenous pyrogens are produced by the host, usually in response to the initial stimulus that is usually triggered by infection or inflammation.
Endogenous pyrogens are polypeptides produced by host cell types, mainly monocytes and macrophages. Endogenous pyrogens, which are produced either systemic or local, managed to enter the circulation and causing fever in central thermoregulation in the hypothalamus.
The majority of exogenous pyrogen is a toxin microorganisms. Exogenous pyrogen of the best known is the group of heterogeneous molecules in all gram-negative bacteria, known as endotoxin. Endotoxin was found in the outer membrane of all gram-negative bacteria and consists of a lipid A and core polysaccharide, attached to a chain-side 'polysaccharide O' consisting of saccharide units are repeated is different for each gram-negative bacteria. Gram-positive organisms also produce a potent exogenous pyrogen. This includes lipoteichoate acid, peptidoglycan, and various exotoxin and enterotoxin. In general, exogenous pyrogens works by inducing the formation of endogenous pyrogen by stimulation of host cells, usually monocytes and macrophages. But the distinction between exogenous and endogenous pyrogens is sometimes difficult to distinguish.

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