Effects of Adrenocorticotropin and Dietary Ascorbic Acid on Delayed Type Hypersensitivity to Human Gamma Globulin in Chickens

Abstract

Three trials were conducted to assess the effects of adrenocorticotropin (ACTH) and dietary ascorbic acid (AA) on delayed type hypersensitivity (DTH) to human gamma globulin (HGG) in chickens. Broiler chicks received AA at 0, 150, or 300 mg/Kg of feed (ppm) continuously from hatching, were sensitized at 5 wk of age to HGG emulsified in complete Freund’s adjuvant, and 2 wk postsensitization, were challenged with an intradermal injection of HGG into a wattle. Birds from each AA group received ACTH at either HGG sensitization, challenge, or both. There were uninjected controls and a vehicle control group, which received gelatin at both sensitization and challenge. The ACTH and gelatin injections were given at 12-h intervals beginning 12 h prior to HGG. Responses to DTH were determined as wattle indices. In all three trials, birds that received ACTH at challenge exhibited a DTH response at 18 and 24 h postchallenge that suppressed, compared with that of controls. Birds that received ACTH at sensitization had a greater wattle response than that of birds that received ACTH at challenge, and this effect was enhanced by dieting AA. In Trial 2, birds that received ACTH at sensitization had a greater wattle response at 18 h post HGG challenge than that of controls.Total leucocyte numbers were unaffected; however, heterophil:lymphocyte ratios were lower in birds that received ACTH at sensitization than in birds that received ACTH at challenge and birds that received ACTH at challenge had fewer lymphocytes. Whether given at challenge or at sensitization, ACTH decreased plasma AA when measured at those times. The 300 ppm level of AA increased plasma AA concentration. Adrenal gland and wattle AA levels were unaffected; however, spleen AA concentration was lower in birds given ACTH at challenge.