Complement fixing activity in diseased human gingival tissues

Human gingival tissue biopsies were classified as “initial or early” or “established or advanced” periodontal lesions on the basis of the histopathological criteria of Page and Schroeder (1976). They were then examined for the ability to fix complement by the anticomplement immunofluorescence technique which detects fixation of exogenously applied guinea pig complement. Complement fixation was found in association with IgG deposits (detected by immunohistochemical staining) in 80 % of the established and advanced lesion, thus suggesting that it was fixed by immune complexes or aggregated IgG. The complement fixing activity was not associated with IgA or IgM deposits. In contrast, less than 13 % of the initial and early lesions were found to contain such activity. The presence of complement fixing activity was thus found to be significantly correlated with the more advanced as opposed to the earlier stages of periodontal inflammation (p = 0.02 by Chisquare analysis).