Three therapeutic areas of clinical immunology that have seen active development recently are immunopharmacology of immunosuppressive drugs; clinical use of the alpha-, beta-, and gamma-interferons and interleukin-2; and monoclonal antibody applications in marrow transplantation and antitumor therapy. Understanding of the immune regulatory systems and of the soluble factors that convey information between immune and related cells (for example, lymphokines and cytokines and their receptors) has improved substantially. New information about established immunosuppressive drugs and the introduction of new drugs are providing new opportunities for effective treatment of autoimmune diseases and improved effectiveness of organ transplantation. Clinical trials are evaluating the use of interleukin-2 in immunodeficiency disorders and neoplastic disease. Monoclonal antibodies, which have been successfully applied to diagnostic procedures, have been shown to be useful for therapeutic applications in marrow transplantation and antitumor treatment.