Immunoglobulins (antibodies) are vitally important proteins which circulate in the blood and perform a wide variety of tasks. They influence markedly the balance of our immune system. The predominant type of antibody in human blood is immunoglobulin G (IgG). The most important tasks are to neutralize and eliminate viruses and bacteria that enter the body, products of bacterial metabolism (toxins) and substances which are formed during inflammation in the body or when cells are destroyed.On account of its structure, IgG is capable of binding to receptors (binding sites) on the surface of blood cells or to certain organ cells and of influencing the behavior of these cells. Cell proliferation and maturation, as well as the activity of cells of our immune system, are regulated in this way. By binding to cells, immunoglobulins have an influence on the control of inflammatory processes, on the regeneration of destroyed tissues after injuries or surgical operations and also on the maintenance of organ functions. They are important for communication between our immune system and our nervous system, for the coagulation and for the system of blood vessels.