HLA-DQ8 mice were immunized with collagen and orally treated with P. histicola. The mice inoculated with P. histicola had a significantly reduced incidence of arthritis as a result of the suppression of the serum levels of several proinflammatory cytokines, such as IL-2, IL-17, and tumor necrosis factor α (TNF-α). Here, TNF is linked to arthritic joint disease.