Antigenicity testing by immunohistochemistry after tissue oxidation
Abstract
Aims: Archived tissue blocks keep antigenicity for a long time under normal storage conditions, whereas tissue sections may show a diminished immunoreactivity over time. Little is known about the processes responsible for antigenicity loss and how tissue sections should be conserved for extended storage. Oxidation and drying are presumed mechanisms. To prove this assertion we provoked degradation of immunoreactivity by chemical oxidation, photooxidation and artificial drying.
Methods: First, paraffin sections of an estrogen receptor (ER) positive breast carcinoma were subjected for variable time periods to hydrogen peroxide, UVA irradiation and dry heat (56°C) prior to ER-immunohistochemistry. Second, using heating and UVA irradiation several other antigens (ER, PR, HER-2neu, p53, p63, p16, PSA, CK5/6, CK7, CK20, SMA, Fli-1, c-kit, CD20, EGFR) were tested, using internal Control TMA sections (iCon-TMAs®).
Results: While hydrogen peroxide had no effect on the ER-staining intensity extended drying showed a detectable diminution after 10 days and UVA irradiation already induced a decrease of immunostaining after 3 days. No entire antigenicity loss was observed. Except for HER-2neu, PSA and Fli-1 all antigens showed at least some diminution, but no entire antigenicity loss after heating and UVA irradiation.
Conclusions: Our study confirms that photooxidation and drying do have influence on immunohistochemistry outcome and provides protocols for testing the stability of specific antigens.
