THE EFFECTS OF ADRENOCORTICOTROPIC HORMONE AND HEAT-STRESS ON THE DISTRIBUTION OF LYMPHOCYTE POPULATIONS IN IMMATURE MALE CHICKENS

This study investigated the effects of heat stress and adrenocorticotr opic hormone (ACTH) on the distribution of lymphocyte populations. Two experiments were conducted; each used 12-wk-old Cornell K-strain male chickens. In Experiment 1, birds were exposed to a temperature of 35 C, 6 h/d for 5 d and control birds were maintained at 24 C. In Experim ent 2, birds received daily i.m. injections of 50 IU/kg body weight of ACTH for 5 d and control birds received .9% saline. On Day 6, blood a nd spleens were collected and lymphocytes were isolated. Indirect immu nofluorescent labeling of lymphocytes were performed to detect B lymph ocytes, CD4+ cells, and CD8+ cells. Neither ACTH injection nor heat st ress affected percentages of B lymphocytes in the blood or the spleen. The CD4+ cells decreased significantly in the blood of ACTH-injected and heat-stressed birds and significantly increased in the spleens of heat-stressed birds. The CD4+ cells in the spleens of ACTH-injected bi rds did not differ from controls. The CD8+ cells significantly decline d in the blood following both ACTH injection and heat stress and signi ficantly increased in the spleen of the ACTH-injected birds but did no t differ from controls in the heat-stressed birds. These results indic ate that stress factors lead to redistribution of different lymphocyte populations.