Effects of corticotropin releasing factor on the production of adrenocorticotropic hormone by leukocyte populations.

1. Corticotropin-releasing factor (CRF), a neuropeptide with immunomodulating properties, is known to stimulate avian splenic leukocytes to produce adrenocorticotropic hormone (ACTH). 2. The present study was to determine which avian splenic leukocyte subpopulation(s) produce ACTH in response to CRF stimulation. 3. Splenic leukocytes from 8-week-old male chickens were isolated on Histopaque 1077 and macrophages were separated from lymphocytes by adherence to a polystyrene surface. 4. Different concentrations of CRF (0, 5, 50, 500 or 1000 ng/m) were incubated with the different leukocyte populations, supernatants were collected and ACTH was measured using a radioimmunoassay. 5. Isolated macrophages, stimulated with CRF, produced significantly more ACTH than either unstimulated macrophages or CRF-stimulated lymphocytes, suggesting that ACTH may be produced by a particular subset of leukocytes, the macrophages (and monocytes), in response to CRF stimulation.