Oral antigens induce rheumatoid arthritis-like inflammation in a rat model

Background and aims The pathogenesis of rheumatoid arthritis (RA) is to be further elucidated. The present study aims to investigate the role of oral antigen in the induction of RA-like inflammation in the articular joints of rats. Methods An RA animal model was developed by gavage-feeding with antigen and aspirin, and lipopolysaccharide intraperitoneal injection. The gut epithelial barrier function was assessed by the absorption of mannitol and lactose. The absorption of the specific antigen was observed by the immune fluorescent method. The frequency of antigen specific CD4+ T cells in the peripheral system was assessed by flow cytometry. The inflammation in the ankle joints was evaluated by light microscopy and immunohistochemistry. Results Rats treated with aspirin showed intestinal barrier dysfunction; high contents of the specific antigen were absorbed into the lamina propria. The antigen specific CD4+ T cells were detected in the spleen that could be activated by exposure to the specific antigen as well as the extracts of joint tissue. High levels of proinflammatory cytokines were detected in the sera. Antigen specific immune complexes were localized in the ankle joints. Heavy extravasation was observed in the synovial cavity. The histology showed an inflammatory feature in the ankle joints. Conclusions Oral antigen can induce RA-like inflammation in the articular joints under certain environment such as gut epithelial barrier dysfunction.