[Mechanisms of release of leucocytic pyrogen]

Mechanisms of the production and release of leucocytic pyrogen (LP) from peritoneal polymorphonuclear leucocytes (PMN) from rabbits were studied in vitro. The following results were obtained. 1) The fever curves of the microsomal and the lysosomal fractions had a later onset and were longer lasting than those from the extracellular fluid. The fever curves of the supernatant of 105,000 g showed the typical response of endogenous pyrogen characterized by a rapid onset and short lasting fever, as shown by the extracellular fluid. 2) The pyrogenicity of LP was the most potent at 60 min while the 105,000 g supernatant was most potent at 30 min after PMN incubation at 37 degrees C. 3) The extracellular protein attained the maximum level at 30 min after incubation of PMN, while the protein content in the supernatant of 105,000 g of PMN decreased gradually to the constant level at 30 min. 4) It was observed that the lysosomal degradation was stimulated with bacterial pyrogen (LPS) at 37 degrees C but LPS did not directly affect the lysosomal fraction of PMN.