Immunomodulatory effects of dietary lipids alter host natural resistance of mice to Listeria monocytogenes infection.

Over the past two decades, unsaturated fatty acids have received particular attention due to their ability to suppress immune functions. Nevertheless, suppression of immune functions also involves a reduction of host natural resistance to eliminate the infectious agents. We have analyzed the role of dietary lipids on immune functions in cells cultured with Listeria monocytogenes. Bactericidal efficiency of peritoneal cells from mice fed a fish oil diet against this bacterium was reduced and the incubation of peritoneal cells with polyunsaturated fatty acids led to similar results. The levels of superoxide radicals in the presence of L. monocytogenes increased in cells from mice fed olive oil or fish oil diets. Proteasome activity, a mechanism that participates in T cell activation, was inhibited in all of the dietary groups assayed in the presence of L. monocytogenes, but this inhibition was abolished in the presence of both MG132 (a proteasome inhibitor) and L. monocytogenes. Overall, these results underline the potential role of fatty acids in the modulation of many functions of the immune system.