Flare-up of antigen-induced arthritis in mice after challenge with oral antigen.

Mice with unilateral chronic mBSA-induced arthritis were orally challenged with mBSA. Three hours after antigen challenge clear flare-up of the chronic arthritis was demonstrable as detected by an increase in the 99mTc uptake of the knee joint and the reaction continued for at least 2 days. The contralateral non-arthritic knee joint was not affected. The dose of mBSA needed to induce a flare-up in nearly all mice within a group was in the order of 20 mg. After oral challenge with 10 or 5 mg of mBSA the incidence was lower and flare-up reactions were only rarely observed after challenge with 2.5 or 1.25 mg mBSA. Histology of knee joints taken at 24 h after oral challenge of 20 mg mBSA revealed an increase in the number of cells in the infiltrate in the synovial tissue and exudate in the joint space, the most conspicuous sign being the increase of PMN. Passage of macromolecules through the gastrointestinal mucosa may be an important principle in the perpetuation of human chronic arthritis.