Tissue fixation methods often result in antigen masking, which subsequently impairs antibody binding and therefore protein detection. The effects of tissue fixation can be partially reversed by performing epitope retrieval, also known as antigen unmasking.
Two types of epitope retrieval have been established; heat based (HIER; Heat-Induced Epitope Retrieval) or enzyme based (PIER; Proteolytic-Induced Epitope Retrieval).
Table 1: Comparison of epitope retrieval methods.
Can be performed using autoclaves, heating plates, hot water baths, pressure cookers, microwaves or steamers (Kim et al. 2016, Ward and Rehg 2014)
Can be performed using enzymes such as pronase, proteinase K, trypsin or pepsin (see IHC protocol 7)
Mode of Action
Restores secondary and tertiary epitope structures
Degrades the peptides masking the epitope
Less popular compared to HIER
Reason: may induce changes to the specimen's morphology
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