Assessment of complement cleavage in gingival fluid in humans with and without periodontal disease

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Abstract
The activation of the complement system may be an important immunopathologic mechanism in the initiation and progression of periodontal disease. The purpose of this study was to assess cleavage of complement components C3 (terminal pathway), C4 (classical pathway) and B (alternative pathway) in gingival fluid obtained from patients with varying types and severities of periodontal disease. Gingival fluid samples were obtained on filter paper strips from 18 healthy sites, 16 gingivitis, 59 chronic adult periodontitis, 45 rapidly progressive periodontitis, and 11 juvenile periodontitis lesions. Each patient was categorized on the basis of age and clinical indices, including Gingival Index, Plaque Index, measurement of pocket depth and loss of periodontal attachment in millimeters, presence of suppuration and bleeding on probing. Cleavage of C3, C4, and B from each site was assessed simultaneously by multilayer crossedimmunoelectrophoresis using solid phase absorbed specific antisera. The mean percentage C3 conversion ranged from a low of 12.6% in the healthy to 90.2% in the juvenile periodontitis group. Statistically significant differences, as determined by the Mann‐Whitney U‐Test, were observed between healthy sites and all other groups, gingivitis and all periodontitis groups, and juvenile vs. chronic periodontitis. C4 was present in all sites examined, but its cleavage product C4c was only observed in sites with juvenile periodontitis. B and its cleavage product Bb were consistently present in gingival fluid from inflamed lesions. The percentage of C3 cleaved to C3c correlated significantly (p < 0.001) with pocket depth (rho=0.58), gingivitis (rho=0.68) and bleeding on probing (rho=0.63). These results suggest that 1) increased complement cleavage is associated with increased severity of inflammation and periodontal destruction, and 2) classical pathway activation does not appear to occur in gingivitis and adult periodontitis, but may occur in juvenile periodontitis.