Effect of treatment with interferon-gamma and concanavalin A on the course of infection of mice with Salmonella typhimurium strain LT-2.

Lymphokines have been shown to affect the resistance of mice to bacterial infections. To explore this effect further, mice were pretreated with 34 units per day for 5 days of a hybridoma supernatant containing primarily interferon-gamma activity. Then, the mice were infected with one LD50 of Salmonella typhimurium strain LT-2. The hybridoma supernatant fluid-treated mice were not protected; in fact, they died faster than did mice only infected with S. typhimurium. When mice were pretreated under the same regimen with pure murine IFN-gamma produced by recombinant DNA technology prior to infection, the mice were protected and 95% survived the infection. The hybridomas had been treated with concanavalin A (ConA) to induce IFN-gamma. When mice were directly treated with ConA prior to infection with S. typhimurium, they also died more quickly than untreated controls. These data suggest that IFN-gamma pretreatment can protect mice against infection with S. typhimurium, but that ConA pretreatment can counteract that effect.