The fact that certain adrenal steroid hormones are immunosuppressive and anti-inflammatory has been known for many years, and is routinely exploited by physicians. These effects are attributable to glucocorticoid steroids such as cortisol. Pharmacological doses of glucocorticoids inhibit most or all T cell types. However we now know that the effect of exposure to raised physiological levels is mainly to drive developing lymphocyte responses towards a Th2 cytokine profile (interleukin-4 secreting) while suppressing the development ofThi (gamma interferon secreting) lymphocytes. Only recently...