GENERAL PRINCIPLES OF IMMUNOSUPPRESSIVE THERAPY
Before describing individual drugs, it is important to consider three principles of immunosuppressive therapy. (1) Primary immune responses are more readily inhibited than are secondary responses. Therefore, components of the primary phase of the immune response, such as pro-cessing, proliferation, and differentiation, will be the most sensitive to drug action. Drugs that are effective in suppressing an immune response in an unsensitized per-son generally will show much less effect, if any, in a sen-sitized individual. Once a population of memory cells has been established, immunosuppressive drugs show little effectiveness. (2) Not all immune responses are equally affected by immunosuppressive drugs. Cellular and humoral immunity may be affected differentially. Additionally, the different classes of immune globulins in a humoral response may be variably affected. (3) Beneficial effects other than immunosuppression may re-sult from therapy with these drugs. In particular, the anti-inflammatory properties of certain of these drugs may be valuable because inflammation often accompanies the immune response. If only an inflammatory reaction is present, a true antiinflammatory drug, such as a corti-costeroid, that is devoid of the many side effects of im-munosuppressive agents should be used.
The focus in the next section is on immunosuppres-sants that have been shown to be clinically useful. Others that may hold promise in the future are men-tioned briefly.