Antigen retrieval: call for a return to first principles

Immunohistochemical Analysis in the Rat Central Nervous System and Peripheral Lymph Node Tissue Sections

Immunohistochemistry (IHC) provides highly specific, reliable and attractive protein visualization. Correct performance and interpretation of an IHC-based multicolor labeling is challenging, especially when utilized for assessing interrelations between target proteins in the tissue with a high fat content such as the central nervous system (CNS). Our protocol represents a refinement of the standard immunolabeling technique particularly adjusted for detection of both structural and soluble proteins in the rat CNS and peripheral lymph nodes (LN) affected by neuroinflammation. Nonetheless, with or without further modifications, our protocol could likely be used for detection of other related protein targets, even in other organs and species than here presented.

The effect of freezing on the immunoprofile of breast carcinoma cells

BACKGROUND

Intraoperative frozen section procedure may be required in some operations performed for breast masses.

AIMS

We investigated the effect of frozen section procedure on the immunoprofile of breast carcinoma cells.

STUDY DESIGN

Cross-sectional study.

METHODS

A total of 53 breast carcinoma cases evaluated with intraoperative frozen sections were included in this study. Immunohistochemically, oestrogen (ER), progesterone (PR) and HER2 primary antibodies were evaluated in both frozen and non-frozen sections of each tumour sample.

RESULTS

No difference was found between the frozen and non-frozen sections in 33 cases in terms of staining rate and intensity of ER, PR and HER2. A decrease was found in the ER, PR and HER2 staining rate (in 10 cases, 9 cases and 6 cases, respectively). Likewise, a decrease was detected in ER, PR and HER2 staining intensity in 6 patients for each. Although there was no staining in frozen sections, immunopositivity was observed in 3 non-frozen sections for ER, in 2 for PR and in 5 for HER2. Statistically, a significant difference was found between the frozen and non-frozen sections in terms of staining rate and intensity for each of the three markers.

CONCLUSION

In this study, the frozen section procedure in breast carcinoma had a negative effect on the immunoprofile. However, considering the importance of hormone receptor status in the treatment, these results should be supported with larger series.

The antigen-antibody reaction in immunohistochemistry

The problems of major concern in immunohistochemical practice are discussed in the following order: (a) the mechanism of the Ag-Ab reaction in fixed tissue as opposed to the in vitro reaction; (b) the chemistry of fixation and its influence on the final result of the immunohistochemical reaction; (c) the various procedures used for antigen retrieval in formaldehyde-fixed tissue; and (d) the consideration of the possible mechanism underlying heat-induced antigen retrieval. Suggestions for further work to attempt a clarification of the mechanism involved in the Ag-Ab reaction in immunohistochemistry resorting to existing histochemical methods for the demonstration of protein side groups are presented, together with some examples already published.

Antigen retrieval techniques: current perspectives

Development of the antigen retrieval (AR) technique, a simple method of boiling archival paraffin-embedded tissue sections in water to enhance the signal of immunohistochemistry (IHC), was the fruit of pioneering efforts guided by the philosophy of rendering IHC applicable to routine formalin-fixed, paraffin-embedded tissues for wide application of IHC in research and clinical pathology. On the basis of thousands of articles and many reviews, a book has recently been published that summarizes basic principles for practice and further development of the AR technique. Major topics with respect to several critical issues, such as the definition, application, technical principles, and further studies of the AR technique, are highlighted in this article. In particular, a further application of the heat-induced retrieval approach for sufficient extraction of nucleic acids in addition to proteins, and standardization of routine IHC based on the AR technique in terms of a test battery approach, are also addressed. Furthermore, understanding the mechanism of the AR technique may shed light on facilitating the development of molecular morphology.