The role of autoantibodies in health and disease.

Serum of healthy individuals contains antibodies that react with self and non-self antigens, generated in absence of external antigen stimulation. These antibodies, called natural antibodies, are particularly IgM isotype, are considered natural autoantibodies (NAA), displaying a moderate affinity for self-antigens. Although incidence of NAA in healthy individuals is not reported, it is established that autoreactive antibodies and B-cells, as well as autoreactive T-cells, are present in healthy persons. The functional abilities of NAA are not clear but is well accepted that they may participate in a variety of activities, such as maintenance of immune homeostasis, regulation of the immune response, resistance to infections, transport and functional modulation of biologically active molecules. On the other hand, specific adaptive immune responses through high-affinity, class-switched IgG autoantibodies, which bind self-proteins, can cause tissue damage or malfunctions, inducing autoimmune diseases. The new technology that allows for more autoantibody screening may further enhance the clinical utility of autoantibody tests, making it possible to diagnose autoimmune disease in its early stages and to intervene before installing injuries. The aim of this review paper is to succinctly analyze the progress in the physiological role and regulatory significance of natural autoantibodies in health and disease.