Heat-induced antigen retrieval formalin-fixed, paraffin-embedded

In 1991 Shi et al. published their seminal observation that high-temperature incubation of formalin-fixed, paraffin-embedded (FFPE) tissue sections in buffers for short periods led to improved immunohistochemical staining.1 However, more than 15 years later, heat-induced antigen retrieval (AR) remains largely an empirical procedure, requiring the optimization of several critical parameters by trial and error.2,3 Further improvements in AR will require an in-depth understanding of the chemistry of formaldehyde fixation and the molecular mechanism(s) underlying the AR method. 

Kawai, K., Serizawa, A., Hamana, T., and Tsutsumi, Y. 1994. Heat-induced antigen retrieval of proliferating cell nuclear antigen and p53 protein on formalin-fixed, paraffin-embedded sections. Pathol. Int. 44 759-764. 

The staining protocol and differences in pretreatment methods are an important factor when formalin-fixed and paraffin-embedded material is nsed, as not all antibodies work satisfactorily under these conditions. Several different approaches can be found in the literature. Heat-induced antigen retrieval by the use of microwave heat treatment has been demonstrated to be more effective in labeling intraneuronal Ap compared to no or enzymatic pretreatment [29]. Information on the use of FA is inconsistent. It is widely used to increase the immunoreactiv-ity of amyloid plaques in AD however, it has been shown that the effect on intraneuronal Ap is low and that use of FA sometimes results in a loss of cellular detail [30]. A recent study tried to quantify the effect of FA pretreatment and analyzed plaque load and intraneuronal Ap immunoreactivity using an APi, antibody in 6-month-old APP/PSIKI mice (Fig. 3 reproduced from [25] with permission from Elsevier). 

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