Omega-3 polyunsaturated fatty acid impairment of early host resistance against Listeria monocytogenes infection is independent of neutrophil infiltration and function.

The primary objective of this study was to determine whether the n-3 PUFA-mediated changes in host response to a Listeria monocytogenes infection (e.g., cytokine production and bacterial clearance) were dependent upon neutrophils. Balb/c mice were fed one of two semi-purified diets that contained either 0 or 41 g of n-3 PUFA/kg. After 4 week, mice were injected with a neutrophil-depleting (RB6-8C5) or isotype-control antibody 24 h prior to infection. Bacterial clearance from the liver and spleen at 3 days post-challenge was measured and the concentration of five pro-inflammatory cytokines in sera 24 h post-infection were determined using a novel protein multiplexing kit. We found that neutrophil depletion impaired bacterial clearance independent of the effect of n-3 PUFA. Interestingly, we observed a rather complex interaction between neutrophil-depletion and n-3 PUFA intake on in vivo pro-inflammatory cytokine production. For example, neutrophil depletion elevated circulating IL-6 and MCP-1 (2- to 5-fold; p<0.05) in n-3 PUFA-fed mice, but less so or not at all in mice fed the control diet. In summary, our data suggest that n-3 PUFA-mediated reduction of host resistance to L. monocytogenes is independent of neutrophil activity.