Mediators and autopathogenic effector cells in proteoglycan-induced arthritic and clinically asymptomatic BALB/c mice

Proteoglycan (aggrecan)-induced arthritis is an autoimmune inflammatory animal model produced in genetically susceptible BALB/c mice. This animal model shows many similarities to human rheumatoid arthritis as indicated by clinical assessments, histopathological studies, and immunological parameters. The systemic immunization of mice with a select group of cartilage proteoglycans provokes immune responses to the immunizing antigen and then the production of cross-reactive antibodies to self proteoglycans. This is followed by an explosive proliferation of autoreactive T cells, especially in joint draining lymph nodes, accompanied by local (joint) inflammatory events. In the current experiments we found that lymphocytes from arthritic, or potentially arthritic but yet clinically asymptomatic animals, produced more IL-2 than those T cells obtained from animals immunized with nonarthritogenic PGs. In addition, synoviocytes isolated from prearthritic or arthritic animals produced several-fold more interleukin-1 beta (IL-1 beta) than cells from normal animals. Flow cytometric analysis indicated an autoantigen (mouse PG)-specific selective proliferation of surface Ig+/CD45R+ cells in prearthritic stages followed by the proliferation of predominantly T helper (CD4+) cells during and after the development of arthritis.