Tolerance to the Induction of Interferons by Endotoxin and Virus: Role of a Humoral Factor.

The intravenous inoculation of either endotoxin or Sindbis virus rendered a rabbit tolerant to the interferon-inducing action of endotoxin or virus. There was crossed tolerance in the sense that animals first inoculated with endotoxin became tolerant to virus. By 6 hours after receiving an inoculation of endotoxin, the animals became tolerant to endotoxin and remained so for at least 3 days, but by the 6th day, sensitivity to endotoxin had been regained. Concurrent with the development of tolerance to endotoxin, a serum humoral factor which could inactivate or decrease the interferon-inducing capacity of endotoxin was found. It is suggested that this factor may play a role in producing tolerance to endotoxin.