[Stimulatory effects of Bacteroides gingivalis fimbriae on production of fibroblasts-derived thymocyte-activating factor (FTAF) by human gingival fibroblasts].

Bacteroides gingivalis (B. gingivalis) is isolated frequently from subgingival plaques of adult periodontal patients. B. gingivalis is a gram-negative anaerobic organism which has fimbriae on its cell surface. In the present study, B. gingivalis fimbriae were examined for their ability to adhere to human gingival fibroblasts (Gin-1), and to stimulate fibroblast-derived thymocyte-activating factor (FTAF) production by Gin-1 cells. The ability of the fimbriae to bind specifically to Gin-1 cells was clearly shown by competition assay between 125I-labeled and unlabeled fimbriae. Significant stimulatory effect of the fimbriae on FTAF production was observed, when the fimbriae were added to Gin-1 cells at a dose of 1 microgram/ml, and this stimulation was observed as early as 24 hr after addition of fimbriae to the cells. It was verified by a spleen cell mitogenic assay for the fimbriae that the stimulatory effect was not due to lipopolysaccharide (LPS) contamination of the fimbriae preparation. The FTAF activity was inhibited about 50% by recombinant human interleukin-1 (IL-1) beta antiserum but not by recombinant human IL-1 alpha antiserum. Therefore, the present study suggests that B. gingivalis fimbriae may play a functional role in the pathogenesis of adult periodontal disease induced by the microorganism.