Dietary Fish Oil Enhances Circulating Interferon-γ in Mice During Listeriosis Without Altering In Vitro Production of This Cytokine

Abstract

The objective of this study was to investigate the impact of feeding mice a diet rich in n-3 polyunsaturated fatty acids (PUFA) from fish oil on the interferon-γ (IFN-γ) response during an active infection with Listeria monocytogenes. Weanling female C3H/Hen mice were fed experimental diets containing 20% by weight one of the following fats: soybean oil, lard, or a mixture of menhaden fish oil and corn oil (17:3, w/w). After 4 weeks, mice were injected with 10⁵ live L. monocytogenes, and the concentration of IFN-γ in serum and spleen was determined 0, 2, 4, and 7 days postinfection by enzyme-linked immunosorbent assay (ELISA). Fish oil-fed mice showed significantly higher IFN-γ in their blood at 2 and 4 days postchallenge compared with mice fed the soybean oil-containing or lard-containing diets (p < 0.001). A higher concentration of IFN-γ was also found in the spleen homogenate of fish oil-fed mice on day 4 postchallenge (p < 0.005). To examine in vitro IFN-γ production, splenocytes were isolated from fish oil-fed and soybean oil-fed mice on day 4 postchallenge and cultured with concanavalin A (1 µg/ml and 10 µg/ml) for 24 and 48 h. There were no significant differences in the IFN-γ concentration in cell culture supernatants between these diet treatments. This study demonstrated that the elevation in the concentration of IFN-γ in blood and spleen during murine listeriosis is accentuated and prolonged by dietary n-3 PUFA, and these effects may not be due to changes in IFN-γ production.