[Inducing tolerance against antigens through initial contact via the mucous membrane]

Mucosal tolerance arises in response to protein antigens that enter through the mucous membranes. This tolerance is unusual in that it becomes systemic and also arises when these antigens subsequently enter the body through the skin or via the bloodstream. Clinical applications of mucosal tolerance are hampered because induction of tolerance does not appear to be possible once systemic sensitisation has taken place. Research into the immunological mechanisms which underlie tolerance induction indicates marked local differences in antigen presentation and the formation of special classes of T lymphocytes which regulate immune reactions. In the future, this knowledge could lead to the application of tolerance in the selective therapeutic down-regulation of immunological diseases such as allergies and autoimmune diseases.