Experimental induction of arthritis in rats immunized with Escherichia coli 0:14 lipopolysaccharide.

ABSTRACT

OBJECTIVE: Escherichia coli 014 (E. coli 014) induces arthritis in rabbits, mice and rats. This study was designed to investigate the effects of lipopolysaccharide (LPS) on the rat arthritis model induced by systemic injections of E. coli 014. METHODS: The induction of arthritis in the ankles of rats immunized by subcutaneous injections with heat-killed E. coli 014 and its LPS was studied. The appearance and levels of serum IgM rheumatoid factor-like substance (RFLS) was also investigated. The localization of interleukin 1 (IL-1) and LPS in the ankle joints were investigated immunohistochemically. RESULTS: The induction rate of arthritis in rats immunized with LPS was the same as that in rats immunized with E. coli. LPS and IL-1 were detected in synovial cells, infiltrating cells and some cells on pannus in arthritic joints. Anti-LPS IgM levels in rats immunized with E. coli were as high as those in rats immunized with LPS. RFLS levels in rats immunized with LPS increased more gradually than those in rats immunized with E. coli. CONCLUSION: Our findings suggest that LPS induces arthritis resembling rheumatoid arthritis in rats. The detection of IL-1 in synovial cells in conjunction with LPS suggests that local stimulation of IL-1 production may play an important role in the induction of this experimental arthritis.