PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) IMMUNOHISTOCHEMISTRY - INFLUENCE OF TISSUE FIXATION, PROCESSING AND EFFECTS OF ANTIGEN RETRIEVAL

The influence of various fixatives and fixation time on Proliferating Cell Nuclear Antigen (PCNA) immunoreactivity in paraffin-embedded sect ions using the rat ileum were compared, and the effect of antigen retr ieval based upon microwave heating in the presence of a solution of sa turated lead thiocyanate was investigated. PCNA immunoreactivity stain ed more intensely when tissues were fixed in Bouin's fluid for 6 hr or methacarn for 3 hr than in 10% buffered formalin or 4% para-formaldeh yde for 3 hr to 1 week, respectively. In general, the number of PCNA p ositive cells and staining intensity decreased as the fixation time wa s prolonged. In sections fixed in formalin for over 24 hr, PCNA immuno reactivity was greatly reduced. Antigen retrieval increased the intens ity of immunostaining in Bouin's, formalin and PFA-fixed tissues, wher eas, methacarn-fixed tissues showed no enhancement. These results sugg est that this technique may alter protein cross-linking caused by alde hydes.