Relationship of complement to experimental arthritis induced in rats with streptococcal cell walls

Experimental arthritis developed in rats injected intraperitoneally with aqueous suspensions of peptidoglycan-polysaccharide complexes (PG-APS) isolated from group A streptococcal cell walls. Reduction of serum complement by pretreatment with cobra venom factor (COV) reduced acute joint inflammation over the first 3 days following injection of PG-APs. Thereafter, the course of the disease was not different in the COV-treated rats. The serum levels of complement were depressed below detectable levels by 24 hr in rats injected only with cell walls, but rebounded to normal levels or above 3 days after injection. In rats injected with COV before cell walls, the complement levels also increased 3 days after injection of cell walls, in contrast to sustained depressed levels in rat injected only with COV. The correlation between severity of joint inflammation and serum complement levels at day 3 was positive in COV-treated rats. The quantity of cell wall per joint at day 3 correlated with the severity of joint disease. However, COV treatment did not alter the amount of cell wall localized in joint tissue. Therefore, although complement does appear to have a role in early joint inflammation, its effect is not upon the transport of cell wall into joint tissue.