[Viewpoints on the pharmacological suppression of immunologic reactivity].

The pharmacological alteration of immunological reactivity is considered. The immunosuppressive drugs may be classified according to their chemical class and their antigen- or cycle-dependency. A relative specificity towards the lymphoid system is cyclophosphamide. New vistas are opened by the modulation of immunological reactivity by cyclic nucleotides. The possibilities afforded by the combined use of immunosuppressive drugs have not been fully exploited. A short therapeutic program including donor antigen, procarbazine and antilymphocyte serum induces immunological tolerance to allogeneic skin grafts in mice and bone marrow allografts in dogs. Immunosuppressive properties of microorganisms are exemplified.