The role of complement in periodontal diseases

The complement system has been implicated as both a pathogenic mechanism and a means of protection in periodontal diseases. It is well known that bacteria activate complement; such activation can initiate a number of events, including bacterial opsonization and killing, release of inflammatory agents, and modulation of other immune reactions. Cleavage of complement proteins has been observed in gingival fluids from individuals with periodontal disease and some investigators have observed complement deposition in diseased gingival tissues. Furthermore, a number of bacterial from individuals with periodontal diseases have been found to activate complement in vitro; some of these organisms appear to have the capacity to evade opsonization due to their proteolytic capacity. However, concrete evidence is not yet available that indicates that complement activation occurs in human periodontal disease and is important in either its pathogenesis or in protection against bacterial virulence factors.