[Effect of dexamethasone-A synthetic glucocorticoid hormone on the immune response in pigs]

These experiments were designed to study the effects of a synthetic drug--dexamethasone (DEX) on the immune response of weaned pigs against viral antigen (hog cholera vaccine) and bacterial antigen (formalin inactivated Salmonella enteritis vaccine). Twenty-three five-week-old pigs were divided into eight groups, six of which were injected twice daily with DEX at 1.0 mg or 0.1 mg per Kg of body weight for either four or five days. The other two groups served as controls. During this period, the two 0.1 mg/Kg DEX-treated groups were injected with live hog cholera vaccine at 1.0 or 0.1 dosage respectively. This same treatment was applied to the two 1.0 mg/Kg DEX-treated groups. One control group was injected with a dose of hog cholera vaccine, while the other was given 1.0 ml of Sal. enteritis vaccine. The hog cholera antibody response in DEX-treated pigs was significantly suppressed (p less than 0.01). However, consistent levels of antibody titers were maintained, indicating a slight antibody production. But in pigs injected with one tenth of the normal dose of hog cholera vaccine, there was little or no immune response (p less than 0.01). A comparison of the response of pigs given different levels of DEX concentrations to those with different doses of hog cholera vaccine showed that dexamethasone significantly suppressed antibody production when antigen concentrations were lower. Significant suppression of agglutinating antibody in response to bacterial antigen was also observed at 14 days post-vaccination (p less than 0.05).