Fixation 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.

Protocol: Unmasking Hidden Epitopes with Proteases Protocol