In immunohistochemistry, what does the term "antigen retrieval" refer to?

Antigen retrieval is a crucial technique in immunohistochemistry that is employed to enhance the visibility of specific antigens in tissue samples, particularly those that may be obscured during the fixation process. During tissue preservation, especially with formalin fixation, certain epitopes (antigenic determinants) can become masked, making them less accessible to antibodies during staining procedures.

The process of antigen retrieval typically involves using heat (such as boiling or microwaving) or enzymatic treatments that help to denature proteins and expose these hidden epitopes. By restoring the conformation of the antigens, researchers and technicians can achieve more specific and sensitive staining results, leading to better visualization of the proteins of interest in histological sections.

The other options pertain to different processes in histopathology: removing excess dye is about the staining cleanup, labeling with fluorescent markers involves a different methodology in microscopy, and fixing tissue samples is a preliminary step in tissue processing rather than a retrieval technique. Thus, the correct understanding of antigen retrieval is essential for effective immunohistochemical analysis and interpretation.