Fixation requirements for the immunohistochemical reactivity of PCNA antibody PC10 on cryostat sections

In contrast to that in paraffin-embedded tissue, the reactivity of monoclonal PCNA antibody PC10 on cryostat sections requires a special fixation procedure as the target epitope is seemingly not accessible to its antibody. A panel of 18 fixation protocols was investigated. Chilled methanol or acetone, or PLP (paraformaldehyde-lysine-periodate) was found to be unsuitable for skin preparations. A two-step fixation protocol was developed for normal skin and basal cell carcinomas. They were fixed first in 3.4% buffered formaldehyde, followed by fixation in 2:1 v/v ethanol-acetic acid. Following this fixation regime, cryostat sections displayed the same PCNA/PC10 labelling pattern as paraffin sections of formalin-fixed tissue.