Preparing Paraffin Tissue Sections for Staining

Most histological studies are performed on formalin-fixed, paraffin-embedded (FFPE) tissue samples. Therefore, there is an extensive atlas of most tissues and organs prepared from these sources, and comparing the location of antigens to these data is immediately informative. Fixation and embedding procedures for preparation of paraffin tissue sections are described here. Because of the harsh fixation, embedding, and preparation conditions used in this procedure, many antigens are not well preserved. Thus, cell staining of paraffin-embedded tissue sections usually requires sensitive detection methods and may require amplification using multiple-layer techniques. The protein cross-linking associated with these fixation conditions can mask epitopes. To uncover them and thus improve antibody-antigen binding, the epitopes can be unmasked by reversing the protein cross-linking. One thermal method, heat-induced epitope retrieval, is presented here.