Antigen retrieval in cells and tissues: enhancement with sodium dodecyl sulfate

Immunocytochemistry provides important information on the localization of antigens in cells and tissues. However, the procedures used to prepare cells and tissues for immunocytochemical labeling may have deleterious effects on the results achieved. That is, the antigen of interest may be difficult or impossible to detect following labeling. These sorts of observations have led to the concept of antigen masking in which the antigen (or specific epitope) is hidden from antibodies specific for that antigen (or epitope). Various procedures to circumvent this problem have been developed. These different procedures generally fit under the term "antigen retrieval" (or epitope retrieval). The practice of antigen retrieval is widely employed with paraffin-embedded material. Antigen retrieval is less often applied to cells and tissues that are not embedded in paraffin. However, in the latter preparations there are situations in which the observed immunolabeling achieved falls short of expectations. This poor level of immunolabeling may, in some situations, be improved upon with antigen retrieval procedures. In this review, we describe experimental situations in which immunolabeling fell short of expectations. We also describe a procedure that has been useful in enhancing immunolabeling efficiency in these cases. The major feature of this procedure is the incorporation of a permeabilization/denaturation step using sodium dodecyl sulfate. This postfixation and prelabeling step dramatically improves immunolabeling for a number of antigens in both cells and cryosections of tissue.