Humoral immune-mediated acute, antigen-induced arthritis in rats is suppressed by the inducing antigen administered orally before, but not after, immunization

Acute ovalbumin-induced arthritis (OIA), which is mediated by Arthus reacti on to ovalbumin (OVA) in the joint space, can be induced by immunization of rats with OVA followed by the intraarticular injection of OVA. Because ora l administration of antigen induces immunological unresponsiveness. we stud ied for the first time the effects of oral administration of OVA on acute O IA. The oral administration of OVA before immunization significantly suppre ssed the development of acute OIA, in accordance with decreases in both the anti-OVA IgG antibody production and in vitro lymphocyte proliferative res ponses to OVA. However. the oral administration of OVA after immunization d id not show any decrease in antibody production or in vitro lymphocyte prol iferation to OVA, or in the severity of acute OIA. These results indicate t hat the induction of oral tolerance to OVA in OIA is possible by oral admin istration of OVA before, but not after, immunization with the antigen. This supports the concept of using antigen feeding as a treatment for certain h umoral immune-mediated diseases.