Enhanced elimination of Listeria monocytogenes at the site of delayed footpad reaction.

The protective activity against a challenge infection with Listeria monocytogenes was investigated at the site of a delayed footpad reaction in mice immunized with viable or killed listeria. Delayed footpad reactivity was induced only in mice immunized with viable bacteria. Rapid and marked elimination of challenge bacteria was observed only at the site of reaction in mice immunized with viable bacteria but not in mice immunized with killed bacteria. Macrophage migration inhibitory activity was observed equally in both groups of mice. These results suggest that the delayed footpad reaction contributes directly to the elimination of bacteria irrespective of macrophage migration inhibitory activity.