Effect of Cortisone on Mouse Resistance to Intravenous Toxicity of Influenza Virus. ∗ †

Summary

1. Treatment of mice with cortisone significantly reduced their resistance to the intravenous toxicity of PR8 influenza A. Lee influenza B, and Newcastle disease viruses. 2. Deaths of cortisone treated mice were prevented by mixing specific immune serum with the viral inoculum or by passive immunization of mice prior to challenge. Immune serum injected intravenously 15 minutes after challenge gave some protection but was without effect when injected 3 hours after challenge. 3. For full effect, closes of 2.5 mg of cortisone had to be used when treatment was begun 24 hours before challenge. Smaller doses were effective if begun earlier. Doses as large as 5.0 mg had no significant effect if given only 3 hours before challenge.