Using paraffin-embedded tissue sections of liver cancer obtained from autopsy which had been preserved in 10% buffered formalin solution for 6 months while PCNA immunoreactivity was lost, we examined the effects of heat processing by either microwave(MW) and autoclave(AC) in the presence of various processing solution. It appeared that AC processing took shorter time period than MW irradiation to restore equal immunoreactivity. With regard to immunoreactivity retrieval by MW irradiation,however, variation of the degree of retrieval depending on processing time was smaller than in AC, and so the stable consequences were obtained. Although AC processed tissues tended to be stained deep, prolonged processing time presented strong background staining and blurred nuclear margins which made it difficult to estimate the positive cell count. As for the effects of processing solution, there was little difference in retrieval of PCNA among 0.01 M citrate buffer (pH 6.0), saturated solution of lead thiocyanate and distilled water, but the least background staining was observed with distilled water. These observations suggest that MW irradiation of which effect of retrieval is less dependent of processing time and with the least background stainability, is superior to AC processing for PCNA immunoreactivity retrieval on formalin-fixed tissues.
immunohistological staining (免疫組織染色)
formalin fixation (ホルマリン固定)