Effect of cortisol on cutaneous basophil hypersensitivity to phytohemagglutinin in chickens

Three independent trials were conducted to determine if cutaneous basophil hypersensitivity (CBH) to the mitogen phytohemagglutinin (PHA-P) was affected by the injection of cortisol in broiler cockerels. Trials 1 and 2 were similar, and Trial 3 imposed a period of heat stress in combination with cortisol. At 6 wk of age, chicks were injected intramuscularly with 2 mg of cortisol in a corn oil vehicle/500 g body weight at 48, 36, 24, and 12 h prior to challenge with PHA-P. Controls received an equal amount of corn oil on the same schedule. Each chick received .05 mL of PHA-P (100 micrograms) in the right wattle and an equal volume of saline in the left wattle. The CBH was assessed by measuring the thickness of wattles at various times from 0 to 48 h after challenge with PHA-P. Wattle indices were calculated. Birds were necropsied at 48 h post-PHA-P, and bursa of Fabricius, spleen, and both adrenals excised and weighed. Cortisol produced a significantly greater CBH response in Trials 1 and 2 as indicated by higher wattle indices at 48 h and at 6 h in Trial 3. Regression analysis indicated significantly greater intercepts for the cortisol responses in Trials 1 and 3 and a significantly greater linear component for the cortisol response in Trial 2. Body weights and relative bursa and spleen weights were reduced significantly by cortisol, whereas relative adrenal weights were increased significantly in Trials 2 and 3. These data indicated that cortisol enhanced CBH to the mitogen PHA-P in broiler cockerels. This is in contrast to reported immunosuppressive effects of other glucocorticoids.