Intracellular localization of bacterial lipopolysaccharide using the avidin biotin complex method at the electron microscopic level.

The intracellular localization in 3T6 fibroblasts of Escherichia coli lipopolysaccharide (LPS) using the rapid avidin-biotin-immunoperoxidase technique at the electron microscopic level was studied. The role of bacterial endotoxin in the etiology of periodontal disease has been well documented previously. The purpose of the present study was to localize LPS within the cell, thereby determining which organelles concentrate the material and relate this to the cytologic pathophysiology. An increased concentration of LPS was found in the cell nuclei and, specifically, in association with nuclear chromatin and nucleoli. The concentration of LPS in the nucleus was directly related to the time of incubation, with some product appearing in that site within 2 minutes. There was no specific localization of endotoxin in mitochondria, lysosomes, Golgi, endoplasmic reticulum or ribosomes. These results imply that bacterial endotoxin may have a direct effect on nuclear components of fibroblasts. The relationship of these results to the etiologic mechanisms of periodontal disease is discussed.