Protease Digestion Step in Immunohistochemicai Procedures: Ficin as a Substitute for Trypsin

Abstract

Aldehyde fixation produces covaient bonding that tends to mask antigenic sites and therefore hampers the immunohistochemicai localization of antigen. Pretreatment with proteases (most commonly trypsin) is used to expose antigenic sites. Ficin, a wide-range protease of vegetable origin, is a satisfactory substitute for trypsin and can be purchased in a ready-to-use, stable solution. Pretreatment with proteases greatly increases the loss of sections during the staining procedures, but this untoward effect is practically eliminated when poly-L-lysine–coated slides are used.