The effect of route of immunization on the lapine immune response to killed Pasteurella haemolytica and the influence of aerosol challenge with the live organism.

Appearance of anti-Pasteurella haemolytica antibody in the serum and broncho-alveolar washings of rabbits is independent of the route of immunization and is similar in both locations. The most influential factor in development of a humoral response is exposure to live P. haemolytica and prior exposure to the killed bacterium has no significant effect upon titre determined following aerosol challenge with live organisms.