Stress, immune reactivity and susceptibility to infectious disease.

Psychological stress is known to affect immune function and to predict infectious disease susceptibility. However, not all individuals who are stressed develop disease. In the present article, we report on a series of studies from our laboratory describing interindividual variability of immune responses to psychological stress. In our initial series of experimental investigations, we demonstrated that acute laboratory stress alters both quantitative and functional components of cellular immunity. An examination of response variability revealed that individuals differ substantially in the magnitude of these immune responses. These differences were found to parallel (and be predicted by) interindividual variability in stress-induced sympathetic nervous system activation. Further investigation revealed that individuals vary consistently in the magnitude of their immune responses to stress, making it conceivable that individual differences in immune reactivity provide a vulnerability factor mediating relationships between stress and disease. In support of this possibility, we have recently reported initial evidence that individual differences in the magnitude of stress-induced reduction of immune function may be of clinical significance, being related to an immune response relevant for protection against infection, antibody response to hepatitis B vaccination.