Acute stress enhances while chronic stress suppresses cell-mediated immunity in vivo: a potential role for leukocyte trafficking.

Delayed type hypersensitivity (DTH) reactions are antigen-specific, cell-mediated immune responses which, depending on the antigen involved, mediate beneficial (resistance to viruses, bacteria, fungi, and certain tumors) or harmful (allergic dermatitis, autoimmunity) aspects of immune function. We have shown that acute stress administered immediately before antigenic challenge results in a significant enhancement of a skin DTH response in rats. A stress-induced trafficking or redeployment of leukocytes to the skin may be one of the factors mediating this immunoenhancement. Here we investigate the effects of varying the duration, intensity, and chronicity of stress on the DTH response and on changes in blood leukocyte distribution and glucocorticoid levels. Acute stress administered for 2 h prior to antigenic challenge, significantly enhanced the DTH response. Increasing the duration of stress from 2 h to 5 h produced the same magnitude enhancement in cutaneous DTH. Moreover, increasing the intensity of acute stress produced a significantly larger enhancement of the DTH response which was accompanied by increasing magnitudes of leukocyte redeployment. In contrast, chronic stress suppressed the DTH response when it was administered for 3 weeks before sensitization and either discontinued upon sensitization, or continued an additional week until challenge, or extended for one week after challenge. The stress-induced redeployment of peripheral blood lymphocytes was attenuated with increasing exposure to chronic stress and correlated with attenuated glucocorticoid responsivity. These results suggest that stress-induced alterations in lymphocyte redeployment may play an important role in mediating the bi-directional effects of acute versus chronic stress on cell-mediated immunity in vivo.