Neutrophils and tumour necrosis factor-alpha are important for controlling early gastrointestinal stages of experimental murine listeriosis.

The present study examined the need for neutrophils and tumour necrosis factor-alpha (TNF alpha) for early defence against gut infection with the enteroinvasive, facultative intracellular bacterial pathogen, Listeria monocytogenes. Mice were treated with a neutrophil-depleting monoclonal antibody (MAb) or a MAb directed against TNF alpha, and the consequences of these treatments on the course of orally initiated infection with the pathogen were monitored. By day 3, orally initiated L. monocytogenes infection in mice treated with either MAb was severely exacerbated to the extent that up to 5000-fold more listeriae were recovered from the walls of the stomach, small intestine, caecum or large intestine of treated mice than from controls. Systemic infection resulting from the ingestion of L. monocytogenes was also severely enhanced in mice treated with these MAbs. Therefore, the results showed that neutrophils and TNF alpha have a critical role in the early defence against enteroinvasive L. monocytogenes infection initiated by a natural (in this case the oral) route, as well as in the control of subsequent systemic infection.