Ovine corticotropin-releasing factor increases endocrine and immunologic activity of avian leukocytes in vitro

Gene array analysis of adrenal glands in broiler chickens following ACTH treatment

BACKGROUND

Difference in adaptability responses to stress has been observed amongst bird species, strains, and individuals. Components of the HPA axis, one of the internal systems involved in homeostasis re-establishment following stress, could play a role in this variability of responses. The aim of the present study was 1) to identify genes involved in the regulation of adrenal activity following ACTH stimulation and 2) to examine adrenal genes differentially expressed in individuals with high and low plasma corticosterone response following ACTH treatment.

RESULTS

Analysis with 21 K poultry oligo microarrays indicated that ACTH treatment affected the expression of 134 genes. Several transcripts assigned to genes involved in the adrenal ACTH signaling pathway and steroidogenic enzymes were identified as differentially expressed by ACTH treatment. Real-time PCR on 18 selected genes confirmed changes in transcript levels of 11 genes, including MC2R, CREM, Cry, Bmal1, Sqle, Prax1, and StAR. Only 4 genes revealed to be differentially expressed between higher and lower adrenal responders to ACTH treatment.

CONCLUSION

The results from the present study reveal putative candidate genes; their role in regulation of adrenal functions and adaptability to stress should be further investigated.

Changes in blood and spleen lymphocyte populations following antigen challenge in immature male chickens

1. The effects of antigen (Ag) injection on the distribution of lymphocyte populations of Cornell K-strain male chickens were studied. 2. Two experiments were conducted. In the first, chickens were injected with Brucella abortus (BA), a purported T-independent antigen. In the second, chickens were injected with sheep red blood cells (SRBC), a T-dependent antigen. Peripheral blood lymphocytes (PBL) and spleen lymphocytes isolated at 0, 3, 6, 9, 12 and 24 h following Ag injection were stained with monoclonal antibodies (mAb) detecting B-lymphocytes, CD4+ and CD8+ cells. 3. B-lymphocytes in the blood or spleen showed no significant changes following either BA or SRBC injection. In contrast, CD4+ cells were decreased in the blood and increased in the spleen following BA and SRBC injections. CD8+ cells were decreased in both blood and spleen following BA injection but were unchanged in either blood or the spleen following SRBC injection. 4. These results indicate that there is a change in both spleen and circulating lymphocyte populations, especially T-helper cells, following Ag injection. T-helper cells are apparently the primary population involved in the initiation of humoral immunity.

Gordon Memorial Lecture. Stress, strains and resistance

1. Stress describes the bird's defence mechanisms and a stressor is the situation that elicits the defence response. 2. As the environment can be viewed as a composite of interacting stressors, the bird's success in coping with its environment depends on the severity of the stressors and the physiological ability to respond properly and thus maintain homeostasis. 3. The neural, endocrine and more recently immune systems are considered to be integrators of the stress response. Although stress responses may be necessary for survival in wild bird populations, they are often detrimental to efficient growth, skeletal integrity and disease resistance in domesticated fowl. 4. Stress responses are modified by the genetic components.

Validation of an assay to measure adrenocorticotropin in plasma and from chicken leukocytes

A RIA for mammalian adrenocorticotropic hormone (ACTH) was modified and validated to measure chicken ACTH. The assay was capable of detecting an increase in chicken plasma ACTH following treatments known to increase plasma ACTH. Both splenic and peripheral blood leukocytes stimulated with corticotropin-releasing factor (CRF) showed a significant increase in ACTH production compared with unstimulated leukocytes. This finding supports the conclusion that the substance produced by leukocytes previously shown in our laboratory to stimulate adrenal cells to secrete corticosterone is immunoreactive ACTH.

The endocrine function of the immune cells in the initiation of humoral immunity

The endocrine functions of different hormones are well documented. Recently, however, evidence of the immune function of several hormones has been accumulated. These findings raised the possibility that immune cells might secrete hormones and in turn self-regulate different immune functions. Indeed, immune cells have been found to secrete different peptide and protein hormones. Adrenocorticotropin hormone (ACTH) is the most studied and was found to be secreted by lymphocytes. In the present authors' laboratory, it was found that not only do lymphocytes secrete ACTH but also that circulating concentrations of corticosterone increased following antigen challenge. It was also observed that at the time of the increased corticosterone, there was a redistribution of different lymphocyte subpopulations from the blood to spleen, the site of antigen presentation and antibody production. It was concluded that the endocrine function of lymphocytes might be important in the initiation of antibody production in chickens.