The febrile responses in rabbits and rats to leucocyte pyrogens of different species.

Abstract

1. We have investigated the effects on body temperature of rats and rabbits of leucocyte pyrogen derived from the blood of rat, rabbit, ox, pig and baboon. 2. In the rabbit intravenous injections (3.5 ml.) of solutions containing leucocyte pyrogen derived from ox, pig and rabbit blood produced fevers with short latencies; no fevers resulted from injections of similar solutions derived from rat or baboon blood. 3. In the rat intraperitoneal injections (2.0 ml.) of solutions containing leucocyte pyrogen derived from ox blood caused a fever, while pig leucocyte pyrogen produced a marked hypothermia. Neither rabbit, baboon, nor rat leucocyte pyrogen had any significant effect on rectal temperature of the rats. 4. Our results show that there is a variability of response in the rat and the rabbit to injection of leucocyte pyrogen of different species; leucocyte pyrogen may be species specific.