EFFECTS OF ANTIGEN RETRIEVAL BY MICROWAVE-HEATING IN FORMALIN-FIXED TISSUE-SECTIONS ON A BROAD PANEL OF ANTIBODIES

Formaldehyde fixation of biopsy specimens for routine purposes has oft en been held responsible for the poor reproducibility of immunohistoch emical studies. Recently, antigen retrieval (AGR) using microwave irra diation was described as a potential tool to enhance immunostaining. A comparison of conventional staining and staining after microwave heat ing was performed for 52 markers, using tissues fixed in formaldehyde for 24 h, 1 to 6 weeks and 3 years respectively, as well as consultant case material. After adequate duration of fixation (24 h), only a few markers (17%) showed better results after AGR, but this percentage wa s increased to 50% when tissues were fixed for longer periods. Maximal enhancement was obtained in the group of consultant cases (58% of tes ted markers demonstrated better staining results), in which the period of fixation and tissue processing was unknown. To achieve reliable en hancement with AGR, continuous heating (100 degrees C) should not be s horter than 20 min. In conclusion, AGR may become the most important t ool to simplify and equalize immunohistochemical techniques, if critic ally evaluated.