Gingival fluid and serum in periodontal diseases. II. Evidence for cleavage of complement components C3, C3 proactivator (factor B) and C4 in gingival fluid.

1. C3 activation products C3c and C3d can be demonstrated in gingival pocket fluid from patients with severe periodontitis. 2. Quantitatively, C3d levels in GF are comparable to levels attained consequent to immune-complex and tryptic activation of human serum. 3. The alternate pathway of complement activation occurs in the periodontal pocket, as demonstrated by conversion of C3 proactivator (Factor B) to C3-activator Bb. 4. C4 is present in an altered form in some, but not all, GF's. This form is electrophoretically similar to that generated from serum by C1s and several proteolytic enzymes.