Abstract
Beeson (1) has first described on the pyrogenic effect of a substance obtained from polymorphonuclear leucocytes of rabbits which was designated as “leucocytic pyrogen”. Bennett (2) also stated that the nature and action of this substance markedly differed from endotoxin in certain respects. This leucocytic pyrogen has been shown to differ from the originally administered endotoxin in the following respects: 1) It was characterized by the rapid brief monophasic body temperature curve in normal rabbits. 2) Daily repeated injections of endogenous pyrogen did not elicite resistance to its fever producing action. 3) It was relatively heat labile and differed from lipopolysaccharide as bacterial pyrogen. On the other hand, it has been found that during the fever response of rabbit injected with endotoxin, there appeared a pyrogenic substance in the circulating blood stream of the rabbit, and it has been called as an endogenous pyrogen in the blood. The differences between endogenous pyrogen and leucocytic pyrogen were not clearly demonstrated (3). But the study of the releasing mechanism and localization of leucocytic pyrogen in leucocytes might be one step of the study for the pathogenesis of fever. Present report deals with the conditions of the production of leucocytic pyrogen from leucocytes of rabbits and some physico-chemical properties of leucocytic pyrogen in vitro.
