Enzyme-induced epitope retrieval (EIER)
There are instances where proteolytic enzymes are the preferred method of tissue pretreatment. Application time and temperature conditions vary from 5-15 minutes and room temperature to 37-40° C. The following proteolytic enzymes are the most commonly used for exposing certain antigen epitopes:
- 0.1% and 0.25% trypsin, pH 7.6-7.8
- 0.25% pepsin, pH 2.0
- Proteinase K
- Protease XXIV
Proteolytic enzymes are available in concentrated stock to ready to use formats from many commercial sources. Vendors typically provide application instructions. An online Internet search can reveal formulas for the technologist wanting to prepare their own solutions.