Complement lesions in cell membranes from joint effusions of various types of arthritis.

Electron microscopy of differentially centrifuged synovial fluid from patients with differing types of arthritis revealed a few membranes bearing complement lesions. It was shown that this is due to activation of the alternate pathway of complement by leukocytic enzymes. It is not clear where the site of action is in inflammatory exudates; it may be on internal membranes of the cells, as no detectable cytotoxic effect could be found using Rb(86) as a marker for specific release. In addition, lysosomal enzymes have the net effect of inhibiting the hemolysis of indicator cells caused by activation of the alternate pathway by inulin.