Fluorescence labeling of intracellular antigens of attached or suspended tissue-culture cells.

This chapter deals with the detection of antigens located in the interior of isolated cells, in which antibodies can detect their antigens only after fixation and permeabilization of cell structure. Unlike surface antigens, cell structure must be preserved first with a fixative, and the lipid barrier of the plasma membrane must be permeabilized using solvents or detergents. Fluorescence detection enhances the sensitivity of detection of small objects in the cytoplasm of cells because the fluorochrome acts as a point source of light. Because many fixatives preserve the native conformation of fixed antigens, it is important to select antibody reagents that can react with undenatured antigen.