Production of fever and its effects on the host.

Leukocytic pyrogen (LP) is a polypeptide that is released from phagocytic leukocytes and mediates fever, by direct action on the thermoregulatory centers in the hypothalamus. During the mediation a complex series of biochemical events occurs in the hypothalamus, including increases in prostaglandin synthesis. The production of LP by phagocytic leukocytes (predominantly monocyte/macrophage) requires synthesis of protein and new messenger-RNA. Recently, it has been discovered that LP has other direct effects on the host. Amongst these effects are: increases in acute phase reactants, including serum amyloid A protein (SAA); release of specific granule contents from neutrophils in vitro; a similarity (if not identity) to human lymphocyte activating factor (LAF) which is a monokine. Thus, LP may have a much broader role to play in the inflammatory response than just mediating fever.