The ultrastructure of leukocyte emigration through the sulcular epithelium in the beagle dog.

Abstract

An electron microscopic investigation of chronically inflamed beagle gingiva has been carried out in order to gain some insight into the pathogenesis of gingival destruction. Chronically inflamed sulcular epithelium was characterized by the presence of numerous polymorphonuclear neutrophilic leukocytes within the intercellular spaces. Many neutrophils were observed to have disrupted cell membranes with a consequent extrusion of cytoplasmic contents including lysosomal granules. The emigration of neutrophils through the epithelium was coincident with a marked decrease in epithelial cell‐to‐cell contacts such as desmosomes and tight junctions. In addition, the affected intercellular spaces were usually dilated and contained glycogen, granular precipitate and free lysosomal particles. The epithelial cells of inflamed sulcular epithelium contained altered tonofibrils. increased amounts of glycogen and accumulations of lipid droplets. It is suggested that the emigration of large numbers of neutrophils in response to chemotactic stimuli originating from the sulcus may damage the normal cell‐to‐cell relationship of the sulcular epithelium resulting in altered cell differentiation and widened intercellular spaces.