Attempts to correlate interferon induction and activation of natural killer cells by Corynebacterium parvum

Intraperitoneal (i.p.) injection of Poly I:Poly C resulted in high interferon titers in the peritoneal wash fluid and in the serum of mice, which was maximal at 4 to 6 h after injection. In contrast, no interferon could be measured in the peritoneal fluid at various times after injection of C. parvum. Also, all attempts to induce serum interferon by C. parvum were unsuccessful. However, both Poly I:Poly C and C. parvum were causing the activation of Natural Killer (NK) cells in the cell population recovered from the peritoneal cavity. From adoptive transfer experiments, there was no indication that C. parvum induced a soluble mediator causing the activation of NK cells. There was also no indication that the interferon activity in the peritoneal cavity of C. parvum-treated mice might have been masked by the presence of an inhibitory molecule interfering with the antiviral effect of interferon in the assay. Our data may suggest activation of NK cells by C. parvum to be independent of interferon induction. Accordingly, we have observed that the injection of anti-interferon did not abolish NK cell activation by C. parvum. Thus, there is the interesting possibility of an interferon-independent mechanism of NK cell activation. However, we have additionally shown that doses of murine alpha/beta interferon as low as 1 IU per mouse caused a significant activation of NK cells in the peritoneal cavity upon i.p. injection. Thus, interferon itself is extremely potent in activating NK cells.