Intradermal testing of swine to monitor changes in delayed hypersensitivity response

Pigs were tested (intradermal injection) on the abdomen with either phytohemagglutinin (PHA) or PHA and tuberculin. The response to PHA was consistent; double-skin thickness averaged 247% of the preinjection thickness during daily testing. Pigs that were primed with Freund's complete adjuvant had a mean double-skin thickness of 208% for tuberculin and 236% for PHA, indicating that the mitogen induced an antigen-like response. Unexpectedly, injections of dexamethasone (0.1 mg/kg of body weight on 2 days) increased the reactivity to both tuberculin and PHA, indicating that the lymphocyte and macrophage response to dexamethasone in swine may be slightly different than the response reported in other species.