Delayed-type hypersensitivity in mice experimentally infected with Fusobacterium necrophorum

The foot-pad test was performed to reveal the induction of delayed-type hypersensitivity (DTH) to Fusobacterium necrophorum in mice experimentally infected with F. necrophorum. For the foot-pad test, heat-killed cells of F. necrophorum were found to be better than viable bacteria as eliciting antigens. The thickness of foot-pad could be measured properly at 48 hr after administration to the foot-pad of heat-killed bacteria. An intraperitoneal dose of the order of 10(5) or 10(6) of viable bacteria evoked a similar foot-pad response. Peak responses were found on days 4 and 14 after the sensitization. The response was found to be specific. This response could be transferred by spleen cells to genetically homogeneous mice, but not to genetically heterogeneous mice. Serum could not transfer the response to either heterogeneous or homogeneous mice. Thus, these results indicate that DTH could be induced by F. necrophorum.