Glucocorticoids that are released from the adrenal glands in response to stress can have profound effects on the immune system. Here, Don Mason illustrates how genetic variation in the magnitude of such a response can determine susceptibility to an experimental autoimmune disease in rats and discusses the implications for susceptibility to inflammatory diseases in humans. He also addresses the possible long-term effects of glucocorticoids on the balance between the cell-mediated and the humoral aspects of immunity and how this balance may influence the temporal development of an immune reaction.

In the evolution of the immune system, a number of potent bactericidal and cytocidal mechanisms have developed. These reactions are potentially damaging to the host and a variety of immunoregulatory mechanisms may have evolved in parallel to limit them. Since virtually all biological parameters show genetic variation, the level to which an immune response may develop before being checked by these immunoregulatory mechanisms will also be expected to vary from one individual to another. In this article the possible consequences of such variation are examined and illustrated by the effect of genetically determined variation in the glucocorticoid stress response during inflammatory immune reactions.