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Abstract Electron microscopy of differentially centrifuged synovial fluid from patients with differing types of arthritis revealed a few membranes bearing complement lesions. This finding occurred equally in patients with seronegative arthritis as well as in patients with rheumatoid arthritis and positive rheumatoid factor. By incubating effusion leukocytes in vitro with effusion fluid, and peripheral leukocytes with syngeneic serum complement, under conditions in which classical complement activation was inhibited, it could be shown that this finding was through activation of the alternative pathway, by means of lysosomal enzymes. It is not clear where, in inflammatory exudates, is the site of action; it may be on the internal membranes of already damaged cells, as no detectable cytotoxic effect could be found by using 86Rb as a marker for specific release in PMN leukocytes. By means of hemolysis of indicator cells, lysosomal enzyme was found to have the net effect of inhibiting the lysis of indicator cells in the presence of complement activated by the alternative pathway. The interpretation of these findings with relationship to the part played by activation of the terminal sequence of complement in inflammatory processes will be discussed.
Dourmashkin et al. (Tue,) studied this question.