Pharmacological regulation of the immune system.

Immunomodulators include any agent or substance that has an effect on the host immune system. These effects may be stimulatory, suppressive or regulatory. Many drugs, chemicals and microbial products have been identified as having specific as well as nonimmunostimulating properties. The first agent to be used clinically as an immunostimulating drug was Bacillus Calmette-Guerin (BCG). Subsequently, other bacterial derivatives, including Corynebacterium parvum and bacterial lipopolysaccharides, were found to have stimulatory effects. Most research in immunostimulating agents has been done in cancer chemotherapy, where such compounds or preparations have been employed to (hopefully) restore chemotherapeutic agent-induced immunosuppression, and thus prevent the development of community-acquired or nosocomial infections. In contrast to immunostimulants, immunoregulators are traditionally defined as being capable of decreasing an abnormally elevated immune response, and therefore restore defective immune function. However, the differentiation between immunoregulators and immunostimulants is not always clearly defined, as the regulatory effects on the immune system of any particular drug may be multifaceted. Clearly, future research must be directed at defining the specific mechanisms of action of potential therapeutic drugs, and in developing improved molecules to ensure safety and efficacy in the clinical setting.