Glucocorticoids and Cellular Immunity in Vitro Facilitation of the Sensitization Phase and Inhibition of the Ef]~ector Phase of a Lymphocyte Anti-fibroblast Reaction* by Irun

Glucocorticoid hormones are widely used clinically to suppress the rejection of transplanted organs, a reaction in which lymphocyte-mediated cellular immunity, rather than antibodies, is thought to play an important role (1), Cellular immune reactions may be divided into at least two major phases. The first phase is considered to be the inductive or sensitization phase which involves antigeninduced lymphocyte differentiation and proliferation. The second is the effector phase and comprises the expressions of the immune reaction, such as lymphocyte-mediated injury to target cells. Thus, glucocorticoid hormones could depress cellular immune reactions by inhibiting the induction of sensitization and/or by suppressing the effector mechanism of sensitized lymphocytes. Gabrielsen and Good (2) have recently reviewed the immunosuppressive properties of adrenal steroid hormones and other chemicals. They noted the difficulty of distinguishing between the establishment of sensitivity and its expression, in systems used to study cellular immunity reactions. Hence, it has been difficult to assign the immunosuppressive action of glucocorticoids to the inductive and/or the effector phases. Nevertheless, Gabrielsen and Good felt that, in addition to the remarkable effects of glucoeorticoids in inhibiting the expression of sensitization, there was some evidence to indicate that cortisone administered around the time of sensitization probably modifies the sensitization process itself (2).