Unmasking hidden epitopes with proteases

INTRODUCTIONFixation can mask epitopes. However, it is often possible to re-expose them using a gentle incubation with proteases, which removes obstructing structures and allows antibody access, as described here. Many proteases can be used for this procedure, including very crude preparations of proteases, such as pronase. However, using a better-characterized protease, such as trypsin, allows a more controlled reaction and better comparison between experiments. Be aware that any of the antigen retrieval methods should be avoided wherever possible, because they may introduce artifactual false-positive staining. Methods for antigen retrieval are specific for each antibody/antigen combination. No attempts to establish quantitative data following these methods should be considered.