What can occur to antigens with high temperatures and repeated heated paraffin exposure?

• A. Epitopes may be altered, leading to false negative results
• B. Antigens become more robust
• C. There is no effect
• D. They become fluorescent

Answer: (A)

Exposure to high temperatures and repeated heated paraffin exposure can damage antigen sites (epitopes) on tissue. Formalin fixation creates cross-links that mask epitopes, and antigen retrieval uses controlled heating to unmask them so antibodies can bind. When heating is excessive or repeated too many times, those epitopes can be irreversibly altered or destroyed, reducing or eliminating antibody binding and producing false negative staining. The other options don’t fit because heat typically denatures proteins rather than making them more robust, there isn’t a mechanism by which heating would make antigens inherently fluorescent, and there is usually some measurable effect on antigenicity when processing conditions are harsh.