Improved detection of apoptotic cells in archival paraffin sections: immunohistochemistry using antibodies to cleaved caspase 3.

Apoptosis has gained central importance in the study of many biological processes, including neoplasia, neurodegenerative diseases, and development. One of the limitations of many studies is the difficulty of specifically identifying individual apoptotic cells. Of the many specific methods developed to detect apoptotic cells, most are not applicable to histological sections of archival paraffin-embedded tissues. Recently, advances in the understanding of the molecular events in apoptosis have led to the realization that caspase activation is by far the most specific indicator of this cell suicide mechanism. Several publications have reported the development of antibodies directed at neoepitopes that are generated in various substrates through the action of caspases. One of these is that present on activated caspase 3, a ubiquitously distributed caspase that is a main effector caspase of the apoptotic cascade within cells. This study demonstrates the utility of using a recently commercially available antibody to cleaved caspase 3 in archival paraffin sections, suggesting that this may be a highly specific and sensitive method generally applicable to many studies of archival material.