The relationship between the
fever of acute
infection and that following injection of bacterial
pyrogen was studied by administering
pyrogens to animals convalescent from acute
infections. Rabbits surviving dermal
pneumococcal infections or
peritonitis due to Escherichia coli were given
intravenous injections of
typhoid or E. coli
vaccine. They showed no evidence of tolerance to the
fever-promoting effect of these pyrogenic materials. Tolerance did develop in infected animals given daily
pyrogen injections during the course of the
infection. Certain previous observations upon the ability of rabbits to develop tolerance to
pyrogens, the broad nature of the tolerance, and its duration were confirmed. It is concluded that the
pyrogen produced by certain bacteria plays little or no rôle in the production of the
fever of
infection. These findings are compatible with the hypothesis that there is a common factor, perhaps a product of cell injury, underlying the
fever accompanying diseases of various types.