Immunopathological investigations during the course of arthritis induced in rats by Streptococcus agalactiae

A large single intraperitoneal injection of sonicated cells of Streptococcus agalactiae O90R induced polyarthritis in Wistar rats. The arthritis reaction score was monitored according to redness, edema, severity and deformity of rat ankle and wrist joints. The inflammation of joints was confirmed by radiology and histology. Acute arthritis was initiated within 48 h and the chronic form continued for more than 30 days. Although serum immunoglobulin was elevated within 48 h, anti-streptococcal antibody was detected only at later times (by enzyme-linked immunosorbent assay and Arthus-type hypersensitivity reactions) and neither serum nor splenocytes of arthritic rats were able to transfer disease to susceptible, normal rats. From these observations and the finding of streptococcal antigen in joint macrophages (by immunogold labelling) we conclude that arthritis is related to persistent streptococcal fragments rather than to antibody or immune complexes.