| Porphyromonas gingivalis is a gram-negative anaerobic bacterium that causes various forms of periodontal diseases. Like other gram-negative bacteria, it produces outer membrane vesicles by the outgrowth of their outer membrane. The outer membrane vesicles exhibit numerous biological properties ranging from adherence, hemolysis, hemagglutination and proteolysis, which are considered to be important virulence factors for P. gingivalis . The small size (20 to 500 nm) of the vesicles, together with their adhesion and proteolytic activities, indicate that they are capable of penetrating the oral mucosa and enter the underlying vascularized connective tissues. Evidence exists indicating that this most likely occurs. P. gingivalis membrane vesicles contain biologically active substances, such as lipopolysaccharide, muramic acid, and proteolytic enzymes, which are capable of modulating immune responses. Previous studies from this laboratory indicated that P. gingivalis membrane vesicles can inhibit interferon gamma-induced MHC class II surface expression on endothelial cells.; The major objective of this research project was to characterize the molecular mechanism(s) by which P. gingivalis membrane vesicles exert their inhibitory effects on MHC class II synthesis and membrane expression. Results from kinetic experiments suggest that the vesicle-induced inhibition involves the IFN-γ signal transduction pathway. Consequently, reverse transcriptase polymerase chain reaction and Southern blotting were used to examine the transcription of the HLA-DRα and CIITA genes. No transcription of these genes in IFN-γ-stimulated cells treated with vesicles could be detected. |
