Further ultrastructural findings in epithelial cells of hairy leukoplakia

Epstein-Barr virus and multivesicular structures appearing in lesions of hairy leukoplakia have been examined ultrastructurally in serial sections. It was found that both structures probably represent various levels of sectioning of transversely cut cell processes. The so-called viral nucleocapsid having a single membrane results when the plane of section is at right angles to one of the membranes but tangential to the other. While the so-called viral particle having two membranes would result if the plane of section is perpendicular to both the membranes of adjacent cells. The internal electron-dense core probably represents filaments enclosed within these processes and therefore does not represent DNA nucleotides. In addition, these nuclei contained bundles of filaments which probably represented tonofilaments. This was found to be due to tangential sectioning of the nuclear membrane surrounding deep cytoplasmic invaginations which led to the appearance of these filaments as if free within the nucleus.