Restraint stress-induced elevations in plasma corticosterone and β-endorphin are not accompanied by alterations in immune function

A variety of stressors active the hypothalamic-pituitary-adrenal (HPA) axis, thereby resulting in elevated levels of circulating ACTH, β-endorphin and corticosterone. Since these hormones have been shown previously to alter measures of immune function, we determined whether presentation of a stressor which activates the HPA axis produces alteration in immune function. Restraint stress resulted in significantly elevated levels of corticosterone and β-endorphin without affecting either proliferative or cytolytic activities of lymphocytes. At concentrations similar to those achieved during stress, in vivo, corticosterone exhibited a dose- and time-dependent reduction in both lymphocyte proliferation as well as natural killer cytotoxicity, in vitro. β-Endorphin, on the other hand, was without direct or modulatory effects. These results indicate that restraint stress-induced activation of the HPA axis occurs witho-ut accompanying in immune function.