Modulation of infection by gamma interferon treatment following trauma.

Gamma interferon (IFN-gamma) has been shown to be able to modulate several microbiol infections, perhaps as a result of the immunoregulatory properties of this interferon. The present study was designed to determine the efficacy of IFN-gamma treatment in a mouse model of infection that simulates clinical conditions occurring following abdominal trauma. In this model, mice were first infected intraperitoneally with Escherichia coli and then underwent immediate surgical laparotomy. Finally the mice were secondarily infected intramuscularly with Klebsiella pneumoniae. Groups of CBA/J mice received either IFN-gamma or RPMI 1640 medium (controls) subcutaneously. IFN-gamma was administered daily at a dose of 7,500 U, commencing 1 h postlaparotomy and continuing until the second bacterial challenge. Mice treated with IFN-gamma survived significantly longer than controls. The Ia antigen expression of peripheral blood monocytes was severely reduced in animals for 3 days after laparotomy and for 5 days after laparotomy and infection. This drop in Ia antigen expression was prevented in animals treated with IFN-gamma. These data indicate that IFN-gamma had a beneficial effect in a model simulating bacterial infection after trauma and that maintenance of Ia antigen expression in interferon-treated mice may have contributed to the observed therapeutic effect.