Basic immunocytochemistry for light microscopy

Immunocytochemistry may be defined as the identification of a cell- or tissue-bound antigen in situ, by means of a specific antibody-antigen reaction, tagged microscopically by a visible label. Successful immunocytochemistry therefore requires (1) preservation of the antigen in a form that is recognizable by the antibody, (2) a suitable antibody, and (3) an appropriate label. The basic technique was first described by Coons and colleagues (1-3), who employed antibody directly labeled with a fluorescent tag to identify antigen in tissue sections. Since that time, the technique has been refined and expanded enormously. Some significant developments include the use of horseradish peroxidase (4) and alkaline phosphatase (5) as label molecules; the development of many, increasingly sensitive, multilayer detection methods; and exploitation of the strong binding between avidin and biotin in detection techniques (6,7).