[Mechanisms and applications of oral tolerance]

The term oral tolerance (OT) describes the antigen-specific suppression of immune responses following the feeding of the antigen. While some common features with other forms of induction of systemic tolerance have been disclosed, OT can be distinguished by certain immunologic characteristics. Thus, work in experimental animal models revealed the importance of intestinal antigen processing, especially antigen processing in the Peyer's patches, in inducing OT. It has become clear that suppressive T cell cytokines derived from mucosal sites play a major role in mediating OT. The variation of the dose of fed antigen and the modulation of the cytokine milieu both have influences on the underlying immunologic mechanisms active suppression, clonal anergy and clonal deletion following oral antigen uptake. In several animal models of autoimmunity the disease activity can be suppressed by feeding oral autoantigen. Based on these results, recent clinical studies have begun to explore OT as a means to treat autoimmune disorders such as multiple sclerosis, rheumatoid arthritis and diabetes.