Oral desensitization or oral tolerance is induced by giving antigenic peptides by the mucosal route. In man, only the oral route has been used up to now. Experiments in animal models of human autoimmune diseases, have shown that it is not necessary to use the primary antigen responsible for disease induction.

Antigens implicated in secondary immune phenomenon can act similarly by means of the so-called "bystander suppression." Thus, for diseases such as multiple sclerosis (MS) and rheumatoid arthritis (RA), candidate antigens for desensitization are available. Many patients with MS have immunity to myelin basic protein (MBP). A recent controlled trial giving MBP to patients with MS is discussed (Weiner et al., Science 259, p. 1321, 1993). No clear-cut effect was obtained. Collagen II is used to induce experimental arthritis in rats; signs of immunity against it can be found in patients with RA.

Collagen-induced arthritis has been successfully modified in animals by feeding of collagen II. In man, one open, uncontrolled trial and one other placebo controlled blind trial have been reported, and these are discussed (Trentham et al., Science 261, 1727, 1993). These trials suggest that oral desensitization might be useful and devoid of side effects. Subreum is a peptic E. coli extract containing heat shock protein 60. Its efficacy as a disease-controlling agent in RA has been documented (Clin. Exp. Rheum. 11, p. 121, 1993). It is given orally. Data suggesting that Subreum acts by oral desensitization are discussed.

Considering the low incidence of side effects observed with oral desensitization, this therapeutic approach should also be tested in other forms of arthritis and other inflammatory diseases.

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