EFFECTS OF CALPROTECTIN IN AVRIDINE-INDUCED ARTHRITIS

Plasma levels of calprotectin correlate with disease activity and clin ical assessments of arthritis in various rheumatic diseases, and high levels have been demonstrated in the synovial fluid of patients with r heumatoid arthritis. However, the role of calprotectin in rheumatic in flammation is unclear. The purpose of the present study was to investi gate potential intra-articular effects of calprotectin. Calprotectin w as injected into joints of healthy male Lewis rats and into joints of rats in the latency period before onset of avridine-induced arthritis. In addition, a group of animals had IgG antibodies to rat calprotecti n injected into joints before onset of avridine-induced arthritis. Inj ection of 0.2 or 10 mu g calprotectin into the ankles of healthy male Lewis rats resulted in histologically minor and reversible inflammator y changes, but without any circulating antibodies to calprotectin. Fur thermore, animals with 40 mu g calprotectin injected into ankles befor e the expected onset of avridine-induced arthritis had lower scores fo r cellular infiltration than were seen in control joints. This differe nce did not quite reach statistical significance in the two-sided test used. However, the induced arthritis increased in joints injected wit h IgG antibodies to calprotectin. These findings may indicate that inc reased local concentrations of calprotectin are partially protective a gainst avridine-induced arthritis. In contrast, reduced local concentr ations appear to exacerbate the severity of arthritis. Calprotectin ma y thus be involved in the re regulation of inflammatory processes in j oints.