Oral polymorphonuclear neutrophil characteristics in relation to oral health: a cross-sectional, observational clinical study

Polymorphonuclear neutrophils(PMNs) have a major role in the innate immune system. However, little is known about PMN contribution in relation to oral health. The objective of this study was to investigate the numbers and functional characteristics of oral PMNs(o PMNs) compared with circulatory PMNs(c PMNs). Oral rinse and venous blood samples were obtained from 268 systemically and orally healthy volunteers in a cross-sectional observational study. PMN counts, cell cycle analysis and cellular activation state were investigated. Also, reactive oxygen species(ROS) production was analyzed, with and without bacterial stimulation(Fusobacterium nucleatum). In males, 1.2 × 106± 1.0 × 106oPMNs were collected, and showed a tendency to correlate with the levels of gingival bleeding(r = 0.215, P = 0.008). Comparable o PMNs counts were found among females(1.0 × 106± 0.7 × 106). More late-stage apoptotic/necrotic cells were found among the o PMNs(53.1%) compared with the c PMNs(8.5%; Po0.001). Without additional stimulation, o PMNs were more activated than c PMNs, as indicated by higher expression of CD11 b, CD63 and CD66 b, and higher constitutive ROS levels(Po0.001). Notably, in response to bacterial stimulation, o PMNs released comparable ROS levels as c PMNs(P = 0.042). In conclusion, this study provides data on viable o PMNs showing high levels of activation in orally and systemically healthy individuals, free of apparent caries lesions and periodontal disease. These data suggests that although the o PMNs are in a more mature stage of their life cycle compared with the c PMNs, o PMNs are still responsive to stimulation, which indicates their functional potential and possible contribution to a healthy oral ecosystem.