[Role of iron in bacterial infections and microelement immunity]

On the basis of the work presented in this review paper and previous reports in scientific journals, one could make the following conclusions. Bacterial pathogens could multiply in the animal body because they produce iron-binding siderophores that help them to obtain iron from transferrin, lactoferrin or ferritin of their host. The determining factor in the mechanism of iron acquisition is lipopolysaccharide (LPS) of virulent bacteria that by itself or with the help of siderophores provides iron that is an essential microelement for bacterial growth. The crucial role, especially in the acquisition of iron in animal hosts, is played by LPS and it should be considered as the virulent factor of invasive bacteria. In response to bacterial infections or tissue inflammations, animals decrease the availability of iron for the use by invading parasites. Infected animals limit the absorption of iron from the gastrointestinal tract, decrease the presence of iron in their blood and develop fever that lowers the bacterial production of siderophores. These defensive responses produce localized or generalized hypoferremia that becomes an essence of the Microelemental (Nutritional) Immunity. Also, the protective hypoferremia could be produced in response to injections of easily excretable, they neutralize microelemental and acquired types of immunity. Thus, sideriphores of some innocuous bacteria could depress the growth of infecting bacteria or neoplasms by the siderophore-induced hypoferremia Intraperitoneal injections of iron to normal and live-vaccine immunized mice provide infecting bacteria not only with the growth essential nutrilite but, also, they neutralize microelemental and acquired immunities. The iron-resistant immunity of vaccinated mice can be induced by the additional stimulation with heat-killed virulent bacteria that elicit production of antibodies to their virulent factors. The reaction of these antibodies with invading bacteria has to procede the phagocytosis with activated macrophages. Considering the crucial role of protective antibodies in the iron-resistant immunity, this antibacterial defense we named Antibody-Dependent Antibacterial Cytotoxicity.