[Current situation of synthetic immunostimulants].

In the novel field of immunopharmacology, one finds two main classes of potential drugs: immunosuppressive agents (autoimmune disorders, transplantations) and immunostimulants. The latter aim at stimulating the humoral and cell-mediated functions of the immune system, in order to treat various immunodeficiency states and to increase defenses against infectious agents and cancer cells. Some immunostimulants (the so-called adjuvants) enhance the immunogenicity of vaccines. Immunostimulants act directly on various cell populations of the immune system and modulate the production and activity of molecular mediators of the latter (cytokines). From a chemical perspective, one must distinguish between natural macromolecular immunostimulants obtained by extraction or genetic engineering and compounds prepared by chemical synthesis. In the latter class, we find many molecules the structures of which derive from those of natural substances (eucaryotic and procaryotic peptides) and a large number of purely synthetic compounds. The latter belong to a wide variety of chemical families and their mechanisms of action are not always perfectly elucidated. Presently, whereas natural macromolecular immunostimulants (bacterial extracts, cytokines, growth factors) are being increasingly used in human medicine, only a small number of synthetic immunostimulants are beyond the stage of preclinical evaluation or phase I clinical studies.