Human neutrophil migration under agarose to bacteria associated with the development of gingivitis

In clinically healthy gingiva and increasingly with the development of inflammation, neutrophils are found in the gingival tissues and sulcus. This study evaluated the relative ability of bacteria associated with gingival health and developing inflammation to stimulate this increase in neutrophil accumulation. Dialyzed bacterial sonic extracts (BE) in buffer and pooled human serum (PHS) from pure cultures of Streptococcus sanguis, Actinomyces viscosus, A naeslundii, Bacteroides intermedius, Fusobacterium sp and Veillonella sp were tested for stimulation of human neutrophil migration under agarose. In addition, fractions of S sanguis culture fluids (CFs) from Sephadex G-10 chromatography were evaluated. All BE solutions were incubated for 1 hour at 37°C and heat-inactivated prior to testing. All BEs in buffer attracted neutrophils, with the greatest responses seen to S sanguis and B intermedius followed by A viscosus. Migration to all BEs in PHS was greater than in buffer, suggesting that all BEs are capable of generating serum chemoattractants. A viscosus BE activated serum attractants to the greatest degree. CFs of S sanguis, A viscosus, and to a lesser degree, Fusobacterium sp, also attracted neutrophils. Evidence from [³H]FMLP competitive ligand-binding assays indicated that S sanguis CFs contained low molecular weight (<700) chemoattractants, which were probably formylmethionyl oligopeptide-like materials. Of the bacteria associated with health, S sanguis and A viscosus appeared at least as able to generate chemoattractants during growth or with exposure to serum as bacteria associated with gingivitis. This observation suggests that these 'healthy' bacteria, which are found in greater numbers with developing inflammation, may mediate increased neutrophil transmigration in early disease.