Investigation of the effects of stress on the immune system in young developing animals is hampered by many variables such as maternal interactions and physical size of immune organs. Young, precocial domestic fowl were used to overcome these difficulties. Domestic fowl, 14 days posthatch, served as an animal model to investigate the effects of stress (acute social isolation) on a rapidly developing immune system. Group-housed animals were isolated for 30, 60, or 90 min and assayed for numerative and functional changes in immune parameters in spleen and blood. The socially isolated birds showed an increase in body temperature, indicative of stress. The number of leukocytes/ml of blood increased in a time-dependent fashion, but the number of leukocytes in the spleen did not. The stress of isolation resulted in a significant increase in B-lymphocyte mitogen proliferation at 30 min, which decreased with time. Social stress also induced a time-dependent decrease in T-lymphocyte mitogen proliferation, which was significant by 90 min. Associated with changes in mitogen responsiveness was a significant increase in the production of an IL-1-like factor by splenic adherent cells from animals isolated for 30 min, which decreased in a time-dependent manner to return to baseline by 90 min. Thus, young domestic fowl represent a practical model for the examination of the effects of stress on immune function in a developing animal. (C) 1994 Academic Press, Inc.
