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.