Abstract
Serum from adults with and without evidence of past periodontitis was assayed for the presence of antibodies to outer membrane components of Porphyromonas gingivalis. A protein of 47 000 Da in Sarcosyl-insoluble outer membrane preparations was shown to be a discriminatory antigen insofar as serum from 29 of 31 (94 per cent) patients with a history of chronic adult periodontitis contained immunoglobulin G antibodies against this protein compared to four of 24 (17 per cent) serum samples from individuals without disease. The binding of antibodies to this antigen was shown to be F(ab')2 mediated. Type and reference strains of other oral and intestinal anaerobic bacteria were studied to see if the immunoreactive protein of 47 000 Da was exclusive to this species. None of the other microorganisms tested possessed this antigen, indicating that it is specific to P. gingivalis.