Cellular and humoral immune responses in sheep experimentally injected with killed and live Corynebacterium pseudotuberculosis.

Both humoral and cellular immune responses have been found to be operative in sheep experimentally injected with killed and live Corynebacterium pseudotuberculosis. However, immunity to sonicated C. pseudotuberculosis cells was primarily of humoral nature though cellular response was also noted. In contrast, live C. pseudotuberculosis cells evoked primarily a cellular response and the encountered humoral response was of lesser intensity. Challenge experiment revealed that humoral response alone was insufficient to protect, and the use of live cells to induce cellular response enhanced the immune status of sheep. It was also observed that nonvaccinated sheep in a herd can acquire immunity from their vaccinated counterparts suggesting a certain importance of 'herd immunity' in C. pseudotuberculosis vaccination.