Why: To identify a specific organelle or another cellular structure and to mark individual cells, it is necessary to counterstain them in immunocytochemistry/immunofluorescence (ICC/IF) assays.
How: Counterstaining is often performed with dyes or antibodies specific to the organelle or cellular structure of interest. For example, the nuclear counterstaining is carried out by using DNA helix intercalating dyes such as DAPI and Hoechst which can penetrate the cells and nuclei without permeabilization. Similarly, fluorescently-labeled phalloidin is used for counterstaining the cytoskeletal actin filaments and fluorescently-tagged wheat germ agglutinin (WGA) is employed for counterstaining the plasma membranes.
Important Considerations: When choosing counterstaining options in...