Bacteria recovered from dental pulp induce apoptosis of lymph node cells

Abstract

Apoptosis is critical in the pathogenesis of several infectious diseases. The induction of apoptosis was assessed in mouse lymph node cells by four bacteria recovered from infected human dental pulp:Gemella morbillorum,Clostridium butyricum,Fusobacterium nucleatumandBifidobacterium adolescentis. Smaller lymph nodes and smaller numbers of cells were observed after experimental dental pulp infection withC. butyricum, suggesting that this bacterium induces cell death. Apoptosis was evaluated by determination of cell ploidy and detection of DNA degradation in cells cultured with killed bacteria. Paraformaldehyde-killedC. butyricumand heat-killedG. morbilloruminduced substantial cell death, whileF. nucleatumandB. adolescentisinduced cell death at lower levels. No bacterial preparations induced apoptosis in cells from mice genetically deficient for tumour necrosis factor receptor p55 (TNFRp55), implicating this receptor directly or indirectly as a mediator in the process. It was concluded that apoptosis may be induced during periapical lesions of pulpal origin.