Effect of human leukocyte interferon on invasiveness of Salmonella species in HEp-2 cell cultures.

The effect of human leukocyte interferon on the invasiveness of Salmonella and Shigella species in HEp-2 cell cultures was examined. The intracellular and extracellular bacteria were identified by a combination of Nomarski differential interference contrast microscopy and UV incident light microscopy applied on the same microscope. Pretreatment of HEp-2 cells with human leukocyte interferon reduced the number of Salmonella typhimurium and Salmonella paratyphi-B bacteria per cell and the proportion of cells containing bacteria in a dose-dependent manner. Maximum inhibitory effect was observed with ca. 100 U of interferon per ml. The inhibitory effect was neutralized with anti-human interferon globulin. Murine fibroblast interferon did not influence the invasiveness of Salmonella species. Invasiveness of Shigella flexneri was not influenced by treatment of cells with human interferon.