Electron Microscopy Studies on the Immobilization Antigens of Paramecium aurelia

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Abstract
The immobilization antigens of Paramecium aurelia were located in the electron microscope by the use of antibody labelled with electron-dense ferritin. On treatment of fixed whole paramecia with ferritin-labelled antibody, followed by sectioning, ferritin granules were seen on the pellicle and cilia of homologous organisms only. By counter-staining the sections with an electron-dense stain (potassium permanganate + uranyl acetate) the absorbed globulin of the antibody was revealed as a thick fuzz on pellicle and cilia. Antigen was present over the entire surface of the organism with the exception of the gullet area. Transformation from one antigenic type to another, by change of temperature, showed the "new" antigen to appear initially on the pellicle and subsequently on cilia. The ferritin labelling, with counterstaining, proved to be very sensitive; ferritin granules and globulin fuzz denoting "new" antigen appearance were detected at isolated sites on the pellicle and cilia after only 1 hr of growth at the higher temperature. The number of these sites then increased, until the granules and fuzz covered the entire surface of first the pellicle and subsequently cilia. Attempts to study the internal antigens with ferritin-labelled antibody were not successful.