Effect of Microwave Pretreatment on Proliferating Cell Nuclear Antigen (PCNA) Immunolocalization in Paraffin Sections

Abstract

PCNA is a nuclear protein that is intimately involved in DNA synthesis and can be detected immunologically. In addition to the differences between the patterns of PCNA expression generated by different antibodies, the effect of such technical factors as fixation should not be underestimated. In this study we assessed the effect of different fixation protocols on PCNA immunohistochemical expression in the rat small intestine with PC-10 antibody, which performs on routine paraffin sections, and we used a method, previously described, to overcome the loss of immunoreactivity in formalin overfixed samples. Although optimal fixation was achieved with 10% buffered formalin for 12 hr and antigenicity was lost progressively during fixation process in all the aldehyde based solutions, antigen retrieval was possible with microwave (MW) irradiation regardless of the fixative used or the fixation period. Although MW pretreatment unmasked PCNA reactive epitopes and increased the sensitivity of the immunohistochemical detection system, the procedure did not affect the estimation of the proliferating cell fraction present. The MW pretreatment of all paraffin embedded samples may permit retrospective analysis of large numbers of archived tissue with reliable results. (The J Histotechnol 18:11, 1995)

Keywords:

• antigen retrieval
• human breast cancer
• microwave
• paraffin sections
• PC-10
• PCNA
• proliferating
• rat small intestines