Counterstains in IHC refer to staining solutions, which provide additional contract to the antibody. Some counterstains recognize specific cellular structures (e.g. nucleus), whereas others may stain whole cells. Selection of counterstains depends on their compatibility with the applied substrate and on the mounting medium.
Counterstains for chromogen detection
Hematoxylin – commonly used counterstain for intensive blue nuclear staining, suitable for most HRP and AP substrates. Works fine with aqueous as well as non-aqueous mounting media formulations.
Eosin Y – red counterstain staining cytoplasm
Methyl Green - light green counterstain – green nuclear staining solution, which might serve as an alternative to hematoxylin, to be used with non-aqueous mounting media.
Methylene blue – light blue counterstain staining cell nuclei, suitable for mounting with organic solvents-based media
Nuclear fast red - red aqueous counterstain – provides pink nuclear counterstain, suitable for non-aqueous mounting
Hematoxylin and eosin stain kit – nuclear and cytoplasmic counterstain based on Mayer´s hematoxylin