The Effect of Starvation on Acquired Immunity to Mouse Typhoid *

The first attempts in this laboratory to effect active immunization of mice against a B. enteritidis infection with a 60° heat-killed vaccine met with complete failure. Eighteen months later the work was resumed using several types of killed vaccines, each of which produced some degree of immunity, including the 600 vaccine which had given negative results previously. The cause of this discrepancy was not understood at the time. It was unlikely to have been due to differences in the mice, since the same strain, free from enteric infection, had been used in all the experiments. In both cases the infecting dose was given orally, employing the same strain of B. enteritidis. However, there was one definite difference in the technic of the two experiments. In the first tests the infecting organisms were placed on asmall piece of dried bread, one piece being fed to each mouse. In order to have the bread wholly consumed and thus obtain a constant infecting dose, the mice were fasted for 12 hours before being infected. In the second experiment infection was accomplished by merely dropping the enteritidis culture into the mouth from a small pipette, without the prior period of starvation. That starvation may play a role in immunity was indicated by Morgulis,5 who quotes Canalis and Morpurgo as having found that fasting, either before or after the inoculation of pigeons with anthrax, lowered their natural resistance to that infection. However, they found no change in rats under similar conditions. These results were confirmed by London. Starving mice before infection was found by Balfour-Jones' to be a means of making mice susceptible to an organism resembling Erysipelothrix muriseptica. If the animals were not starved the per os administration was without effect. Therefore, to determine whether or not the discordant results obtained in this laboratory were due to the fasting period preceding