Avidin-Biotin Labeling of Cellular Antigens in Cryostat-Sectioned Tissue

Immunohistochemical staining techniques are widely used for the identification of a variety of diverse antigens in paraffin-embedded tissues (1 ). Nonetheless, a major limitation in the use of paraffin-embedded fixed tissue is that many potentially interesting antigens are denatured and their antigenicity destroyed by the process of tissue fixation. To overcome this problem, many laboratories have employed the use of cryostat cut frozen sections (2 – 4 ). The principles of the staining reactions are identical to those used for paraffin sections, and the antigenicity of the majority of cellular proteins and carbohydrate moieties are preserved. The frozen section technique, however, has its own drawbacks. Special equipment is needed for freezing, cutting, and storing the frozen tissue blocks. Second, good morphologic detail requires greater skill in cutting the tissue sections and careful attention to particular steps in the procedure (see Section 3 ). Even under optimal conditions, the morphology of the immunostained frozen section will be inferior to the morphology obtained from paraffin-embedded fixed tissue