Cyclophosphamide-Induced Immunosuppression Demonstrated in Pasteurella multocida-Vaccinated Chickens

SUMMARY Vaccinated cyclophosphamide-treated chickens were more susceptible to challenge infection than were vaccinated untreated chickens. Antibody titers were greatly reduced in cyclophosphamidetreated chickens. The results suggest that the presence of specific antibody is important in determining the ability of chickens to resist Pasteurella infection.