Neutrophil fate in gingival crevicular fluid

The fate of the neutrophils within the inflammatory exudate in the periodontal crevice and their possible participation in the formation of neutrophil extracellular traps (NETs) are of clinical interest. However, the cytological analysis of clinical samples of inflammatory exudate is restricted by the obtainable quantities, which do not enable employing the routine approaches. Clinical examinations, ACLAR strip sampling, scanning electron microscopy, and confocal laser scanning microscopy were employed to analyze purulent crevicular exudate and gingival crevicular fluid in periodontitis. Bacteria, neutrophil activation, NETosis stages, and NETs were identified by molecular probe, expression of citrullinated histone H3, enzymatic digestion, and ultrastructurally. Crevicular neutrophils, all in diverse NETosis stages marked by the histone citrullination, and an abundance of NETs were found in both purulent crevicular exudate and gingival crevicular fluid. Largely varying quantities of dispersed crevicular bacteria were entrapped by NETs, but no phagocytized bacteria were evident in gingival crevicular fluid. The offered method enables for the first time the demonstration NETs in gingival crevicular fluid. The histone citrullination of all the floating crevicular neutrophils indicates that they all undergo NETosis.