Identification of bacteria in immunopathologic mechanisms of human dental pulp

Serial frozen sections from human dental pulp were used for the identification of oral bacteria in immunopathologic mechanisms. Sera raised against Actinomyces viscosus, A. naeslundii, Bacteroides gingivalis, and B. melaninogenicus ss. intermedius, commercial sera against human immunoglobulins, complement, and monoclonal antibodies against human T cells were used in a double-staining immunofluorescence technique. Sections of dental pulp from normal teeth showed no penetration of bacteria or bacterial antigens and no signs of inflammation. A unique aspect of the present study was the demonstration that penetrating bacteria and bacterial antigens in the pulp of involved teeth were always associated with antibodies and frequently also with complement. A. viscosus has been found most frequently in complement-fixing immune complexes followed by B. gingivalis. A. naeslundii and B. melaninogenicus ss. intermedius were found only in complexes with antibodies. The involvement of plasma cells and T cells was also demonstrated. In the dental pulps of diseased teeth, cytotoxic and Arthus type immunopathologic reactions occurred.