Avidin-biotin labeling of cellular antigens in cryostat-sectioned tissue

Advances in immunohistochemical technologies have greatly improved the ability to visualize antigens in formalin-fixed paraffin-embedded tissues. Nonetheless, there are occasions in which there may be no alternative to the use of cryostat-sectioned frozen tissues. While the basic chemistries and techniques used in staining cryostat-sectioned tissues are identical to those employed for staining paraffin-embedded sections, there are some unique issues to consider with frozen sections. Achieving excellent results requires the use of properly prepared and stored frozen tissue blocks embedded in an appropriate mounting compound, properly prepared and mounted cryostat-prepared sections, blocking of endogenous biotin and peroxidases that might interfere with interpretation of specific staining, and a mild postsectioning fixation step. This chapter describes a general frozen-section immunostaining procedure that provides guidelines for handling these special considerations.