CYTOKINE-INDUCING COMPONENTS OF PERIODONTOPATHOGENIC BACTERIA

Pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8 and tumour necrosis factor (TNF) are believed to be the major pathological mediators of inflammatory diseases ranging from arthritis to the peri odontal diseases. The stimuli inducing proinflammatory cytokine induct ion in the former disease is unclear but in the periodontal diseases i t is obvious that the stimulus is the accumulation of bacteria in the subgingival region. As these bacteria do not invade the lesional tissu es in large numbers, it is believed that their soluble components or p roducts interact with host tissues to induce cytokine gene transcripti on. The paradigm is that Lipopolysaccharide is the key bacterial compo nent inducing pro-inflammatory cytokine gene expression. However, over the past decade a growing number of reports on non-oral bacteria have established that many other bacterial components, as well as secretor y products, have the capacity to induce cytokine synthesis. Some of th ese, such as the protein pneumolysin from Streptococcus pneumoniae, ar e incredibly potent (in this case inducing cytokine synthesis at femto molar concentrations). This review surveys the range of bacterial comp onents and products which have been shown to stimulate cytokine synthe sis with particular emphasis on the hypothesis that these components p lay a role in the pathology of the periodontal diseases.