are of bacterial origin and most are able to stimulate the nonspecific immune response by acting on polymorphonuclear cells and macrophages as well as on specific antibody production. They have been shown to stimulate many of the functions of polymorphonuclear cells, specifically the formation of oxygenated free radicals, chemotaxis and adhesion. These cells participate in both the nonspecific immune response (phagocytosis, proinflammatory cytokine production) and the specific immune response (antigen processing and presentation, lymphocyte proliferation). Bacterial immunomodulator have been shown to increase the production of many cytokines (IL-1, IL-6, IL-8, tumour necrosis factor-alpha and colony-stimulating factor), leading to the activation of the cytokine network. They are also able to stimulate natural killer cells involved in antiviral immunity. Bacterial immunomodulator affect the immune system in a very complex way. Numerous clinical trials in the world have confirmed the positive role of bacterial immunomodulator in significantly reducing the number of infections in children and adults. The administration of bacterial immunomodulators should be considered with care to avoid the potential risk of inducing an autoimmune disease.

        Key words: bacterial immunomodulators – respiratory infections – bacterial antigens – cytokines.