Thermal response to zymosan: the differential role of complement.
OBJECTIVE
This study was designed to determine whether the complement (C) system may be involved in the febrile response to zymosan (Zym), a glycan derived from yeast cell walls.


METHODS
Cobra venom factor (CVF) at 100 U/animal or its vehicle, pyrogen-free saline (PFS), was injected intravenously (i.v.) into guinea pigs to deplete serum C. Eighteen hours later, a low or high dose of Zym or its vehicle, PFS, was administered i.v. or intraperitoneally (i.p.) to these animals. The core temperature (T(c)) was measured continuously by thermocouples. Serum C levels were determined by sheep erythrocyte hemolytic assay.


RESULTS
Zym at 1 mg/kg caused a 1 degrees C T(c) rise that was not significantly affected by CVF pretreatment. However, CVF-induced hypocomplementation converted the T(c) fall ( approximately 1.2 degrees C) produced by 100 mg/kg of Zym i.p. into a 1 degrees C T(c) rise. Similarly, CVF pretreatment did not affect the T(c) rise caused by 0.5 mg/kg of Zym i.v., but converted the T(c) fall induced by 25 mg/kg i.v. into a 1 degrees C T(c) rise. A separate experiment showed that 25, but not 0.5 mg/kg of Zym i.v., decreased serum C by 34% in 15 min; C did not recover over the next 6 h. A second i.v. injection of 25 mg Zym/kg 210 min later, when the T(c) had recovered but the serum C had not, yielded a smaller and briefer T(c) fall.


CONCLUSIONS
These results suggest that Zym is inherently pyrogenic, but this effect is manifested only when the dose of zymosan is too small to activate C or when C has been reduced by prior activation.
Li
Shuxin
S
Department of Physiology, University of Tennessee Health Science Center, Memphis, Tenn 38163, USA. lshuxin@physio 1.utmem.edu
Llanos-Q
Jose
J
Blatteis
Clark  M
C
D000818:Animals; D003169:Complement Inactivator Proteins / Q000494:pharmacology; D003165:Complement System Proteins / Q000276:immunology* / Q000378:metabolism; D004546:Elapid Venoms / Q000494:pharmacology; D005334:Fever / Q000139:chemically induced / Q000276:immunology* / Q000503:physiopathology*; D006168:Guinea Pigs; D007113:Immunity, Innate / Q000502:physiology; D007274:Injections, Intraperitoneal; D008297:Male; D012965:Sodium Chloride / Q000494:pharmacology; D015054:Zymosan
D003169:Complement Inactivator Proteins; D004546:Elapid Venoms; C016310:cobra venom factor; D012965:Sodium Chloride; D003165:Complement System Proteins; D015054:Zymosan