FURTHER STUDIES ON PASSIVE TRANSFER OF TOLERANCE TO PYROGENICITY OF BACTERIAL ENDOTOXIN

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Abstract
Treatment of donor rabbits with Salmonella typhosa 0 901 endotoxin for 5 weeks is no more effective than a brief series of injections for demonstrating passive transfer of tolerance to pyrogenicity in normal recipients. A monophasic fever is seen in passively tolerant recipients challenged with 2.5 [mu]g endotoxin, whereas a 25 [mu]g dose results in the biphasic response typical of the normal rabbit. The acute leucopenic response to endotoxin is seen in recipient animals, regardless of magnitude or course of fever. Rabbits injected daily with endotoxin continue to show the acute leucopenia despite the characteristic early pyrogen tolerance. HN2-treated rabbits suffer a rapidly developing, exaggerated endotoxin fever. The implications of these findings for the pathogenesis of endotoxin fever are discussed; the evidence supports the hypothesis that endotoxin produces fever by direct action rather than through endogenous leucocytic pyrogen.