Electron immunocytochemical localization of Actinobacillus actinomycetemcomitans leukotoxin

The Actinobacillus actinomycetemcomitans leukotoxin was localized in A. actinomycetemcomitans bacteria using an electron immunocytochemical thin‐section labeling method. An immuno‐dot blot procedure was initially used to ascertain the optimal specimen fixation. This consisted of a periodate‐lysine‐paraformaldehyde (2%) fixative in a phosphate buffer followed by embedding in LR White. Affinity‐purified toxin was used to produce a monospecific polyclonal antibody. The reaction sites were visualized with a colloidal gold‐tagged reporter antibody. The leukotoxin was found to be localized either in the cell envelope and/or in membranous vesicles on the outer surface of the bacterial cell. These results support previous observations indicating the same location.