Morphological Characterization of Para and Pro-Inflammatory Neutrophil Phenotypes Using Transmission Electron Microscopy

Neutrophils play a crucial role in the immune response, leaving the circulation to participate in an inflammatory response to perceived pathogens. Yet in the oral cavity, they are constantly recruited into the gingival sulcus even in health, producing no apparent clinical inflammation. It has been demonstrated that in this homeostatic state the neutrophils present a “partially active” phenotype, termed para-inflammation. To further investigate this phenotype, we studied the morphology of neutrophils obtained in vivo under transmission electron microscopy (TEM), in health and Chronic Periodontitis (CP), in the blood and the oral cavity. To study and compare the changes induced by the commensal oral bacteria in vitro, blood neutrophils were also incubated separately with S. oralis cultures. Our hypothesis was that the neutrophils in the healthy oral cavity will present a morphology consistent with para-inflammation, in contrast to the naïve phenotype of blood neutrophils, and the fully active, pro-inflammatory oral neutrophils in CP.M.Sc