Examination of host immune resistance against Listeria monocytogenes infection in cyclophosphamide-treated mice after dietary lipid administration.

BACKGROUND & AIMS Despite the beneficial effects in the resolution of inflammatory disorders due to their immunosuppressive properties, n-3 polyunsaturated fatty acids are associated with a reduction of immune resistance to some microorganisms. Here, we examine the influence of different dietary lipids on host immune resistance against Listeria monocytogenes in mice treated with cyclophosphamide (CPA). METHODS Balb/c mice were fed one of four diets, which contained either olive oil (OO), fish oil (FO), hydrogenated coconut oil (HCO) or low fat (LF) for 4 weeks. Subsequently, mice were treated with CPA or PBS, prior to L. monocytogenes infection. Splenocyte proliferation, survival analysis, counts of viable bacteria from spleens and livers, and measurement of pro-inflammatory cytokine levels were determined. RESULTS The FO-rich diet reduced survival, particularly in CPA-treated mice. CPA was responsible for a significant increase of viable bacteria recovery from spleens and livers within each group fed high fat diets, which was aggravated in mice fed an FO diet. In addition, a significant increase of both TNF-alpha and IL-12p70 levels was detected in this group. These results may acquire a crucial relevance in clinical nutrition, particularly when FO diets are administered to immunocompromised patients. CONCLUSIONS The mechanism(s) that impair(s) the elimination of L. monocytogenes could be associated with a low mitogen-stimulated splenocyte proliferation, and with an alteration of pro-inflammatory cytokine production. The application of the neutropenic agent CPA moderately aggravates the immunosuppressive state mainly in FO-fed animals.