Antigen retrieval is a non-enzymatic pretreatment for immunostaining to reduce or eliminate the chemical modifications caused by formalin fixation, through high temperature heating or strong alkaline solution (non-heating).
In medicine, most surgically removed tissue samples are fixed in formalin (4% formaldehyde) and embedded in paraffin to preserve the morphology for review by pathologists using stains and microscopy to make a diagnosis.
Antigen retrieval technique is a non-enzymatic pretreatment for immunostaining to reduce or eliminate these formalin-induced chemical modifications through high temperature heating or strong alkaline solution (non-heating).
[1] Non-heating alkaline-induced antigen retrieval requires immersing slides in a strong alkaline solution (sodium hydroxide and methanol).
Enzyme digestion, also referred to as protease-induced epitope retrieval by some authors, is an old technique used in immunohistochemistry for formalin fixed paraffin embedded tissue sections before the advent of AR.
Disadvantages of enzyme digestion include a low success rate for restoring immunoreactivity and the potential destruction of tissue morphology and the antigen of interest.
Although enzyme digestion and antigen retrieval target the same problem in immunohistochemistry, these two techniques differs in both the mode of action and effectiveness, warranting distinct nomenclature.