Studies on the pathogenesis of fever. XX. Suppression and regeneration of pyrogen-producing capacity of exudate granulocytes

Studies on the production of endogenous pyrogen by rabbit monocytes: the role of calcium and cyclic nucleotides

Rabbit monocytes stimulated with endotoxin produced endogenous pyrogen, even under conditions of high or low extracellular calcium concentrations. Maximal production occurred when the concentration was in the near-physiological range. Prolonged incubation of cells with a calcium chelator prevented subsequent activation with endotoxin, an effect which was rapidly reversible by re-addition of calcium but not other cations. Addition of small amounts of lanthanum, which acts as a calcium channel blocker, prevented the restoration of pyrogen production, indicating that entry of the added calcium into the monocyte was required. Incorporation of a calcium ionophore into the cell membrane did not stimulate pyrogen production, and no measurable influx or efflux of calcium occurred during stimulation with endotoxin. These observations suggest that a slowly exchangeable calcium pool is necessary for the production of endogenous pyrogen, but that a rise in intracellular calcium is not by itself a necessary or sufficient stimulus. This stands in contrast to other biological systems in which Ca2+ directly couples stimulus and hormone secretion. Incubation of cells with agents shown to increase cyclic 3',5' AMP or cyclic 3',5' GMP levels in monocytes similarly did not stimulate pyrogen production or modulate its production by endotoxin stimulation. Thus, cyclic nucleotides also did not play a detectable role as intracellular messengers in this system. Future work is required to define more clearly the mechanism for the production of endogenous pyrogen, given its marked effects on the immune system through lymphocyte activation and temperature regulation.

A rationale for administering leukocyte endogenous mediator to protein malnourished, hospitalized patients

Leukocyte endogenous mediator is a low molecular-weight protein synthesized by circulating monocytes and fixed macrophages of the reticuloendothelial system. Exogenous administration of leukocyte endogenous mediator to a well-nourished animal stimulates both specific and nonspecific immune function and replicates the protein metabolic response to infection, characterized by fever and increased amino acid oxidation, skeletal protein degradation and synthesis of "acute-phase" proteins. Leukocyte endogenous mediator administration also affords protection against semi-lethal doses of bacteremia in the well-nourished animal. In the protein-depleted host, synthesis or release of leukocyte endogenous mediator in response to infection appears to be reduced and the attenuated metabolic response may be attributed, in part, to a deficit in its production. However, nutritional repletion of the malnourished patient results in restoration of the capacity to produce leukocyte endogenous mediator usually within three to seven days, if adequate dietary protein is provided. Since protein malnutrition is associated with increased incidence and severity of bacterial infections, we postulate that the reduced synthesis and/or release of leukocyte endogenous mediator in protein malnutrition is detrimental. In those critically-ill, malnourished patients who cannot endogenously synthesize leukocyte endogenous mediator, and for clinical reasons cannot be repleted rapidly or are already infected and/or undergoing operative stress, exogenous administration of leukocyte endogenous mediator should be considered along with nutritional support. Administration of this protein to a seriously-ill malnourished individual should produce a metabolic profile of fever, increased urinary nitrogen excretion and falls in serum albumin concentrations that are generally considered pathologic. However, administration of leukocyte endogenous mediator over short periods of time should also provide the anabolic impetus for the augmented synthesis of proteins beneficial to recovery.(ABSTRACT TRUNCATED AT 400 WORDS)

Further similarities of endogenous pyrogen and leukocytic endogenous mediator

The release of endogenous pyrogen (EP) from rabbit peritoneal granulocytes was measured with a three-point log dose-response curve. Release of EP was inhibited when the cells were incubated in media containing potassium or calcium. Measurements of leukocytic endogenous mediator (LEM) activity, i.e., lowering of plasma iron and zinc and increases in blood neutrophils, were made on the same supernatant media. When EP release was inhibited there was a similar inhibition of LEM activity. These results indicate a similarity between the release of pyrogenic and LEM activities. Together with previous purification studies, the results suggest that EP and LEM are similar and may be identical factors.