Low-temperature heating overnight in tris-HCl buffer pH 9 is a good alternative for antigen retrieval in formalin-fixed paraffin-embedded tissue

Heat-induced retrieval of antigens masked by formalin fixation in paraffin-embedded tissue is widely used in routine surgical pathology. Microwave heating at high temperature for a relatively short period has been tested extensively. Although good results for commonly used antibodies are obtained by optimizing heating conditions and retrieval solutions, a standard protocol for all antibodies is not yet available. Other problems encountered are affected morphology and loss of tissue attachment to the slides. In this study we elaborated a previously described retrieval method applying conventional heating at a lower temperature for a prolonged time. We tested 16 routinely used antibodies on formalin-fixed, paraffin-embedded tissues, which were stained after overnight heating at 80 degrees C in retrieval solutions varying in pH value. The results were compared with standard microwave heating in a solution of Tris-HCl plus urea pH 9.5. Maximal retrieval was obtained with 14 out of 16 antibodies by overnight heating at 80 degrees C in Tris buffer pH 9. Tissue morphology was well preserved. The results were slightly superior to those obtained with microwave retrieval in pH 9.5 Tris+urea buffer. Tn conclusion, overnight heating at 80 degrees C in Tris buffer pH 9 is a good alternative for retrieval of antigens and is easy to perform.