Ultrastructural localization of gonococcal antigens in infected epithelial cells as visualized by post-embedding immuno-electronmicroscopy.

Since ultrastructural localization of bacterial antigens during infection might considerably contribute to the understanding of the infectious process, we investigated the usefulness of post-embedding immuno-electronmicroscopy in the visualization of neisserial antigens. With the use of proper fixation conditions in combination with ultracryomicrotomy, we have been able to specifically mark gonococcal antigens in ultrathin sections incubated with a polyclonal antiserum and subsequently with gold-labelled protein A. Electron microscopy of cryosections from infected Chang conjunctiva epithelial cells showed that gonococcal antigens could be marked during various stages of the infectious process. With the polyclonal antiserum used there appeared to be no difference in labelling between extracellular and intracellular bacteria, suggesting that the probed antigens were not altered during the internalization process. Our results indicate post-embedding immuno-electronmicroscopy as a useful technique to localize bacterial antigens during the adherence, the internalization and the intracellular degradation of bacteria in host cells.