Histology FAQ

Staining, Histochemistry and Histotechnology

(Frequently Asked Questions)


Dr. John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London, Canada



FAQ Home > Immunohistochemistry

Antigen retrieval: A patented or copyright phrase?


I was talking to someone the other day concerning immunoperoxidase staining and I mentioned the term "antigen retrieval". I was told that the term is patented and that it  was not legal to use the phrase. Has anyone else heard that information. I do know that Biogenex makes and sells "Antigen Retrieval Solution," and we use it in our lab.

Is it really true that we cannot talk or write about antigen retrieval in a general way without the risk of being sued for some infringement of a copyright or a patent?


This was the subject of some heated discussion in the HistoNet listserver in 1998. The following remarks are based on the contributions of people too numerous to acknowledge individually, and are colored by my own conclusions.

On the one hand there were the "common sense" viewpoints making the case that

(a) A combination of two common words could not possibly amount to an original literary composition (with copyright assignable to an author or publisher), and could never be construed as an invention. (A particular solution could, of course, be invented for the purpose of retrieving antigens, and patented.)

(b) Methods for enhancing the detection of antigens in sections have been published in the scientific literature for several years. All involve treatment with water, which may be cold or hot, and most techniques specify other substances to be dissolved in the water. The solutes include detergents (to damage cell membranes, helping large antibody molecules to enter cytoplasm), urea (disturbs protein conformation and may expose "buried" epitopes), a variety of metal salts, notably zinc sulfate and lead thiocyanate (probably work by changing the conformation of the antigen), and all sorts of buffers, mostly pH 5-6 or pH 8-9. (This probably catalyzes hydrolysis of the cross-links that formaldehyde makes between nearby parts of protein molecules. The optimum pH varies with different antigens. Heat accelerates the reaction, and can be conveniently delivered in a microwave oven.)

On the other hand (Would it be the Left or the Right?) were people using these methods daily, in routine procedures, sometimes with a proprietary solution and sometimes varying the technique to suit the antigen. Feeling their freedom of expression (and perhaps also their livelihoods) threatened, they suggested alternatives to "antigen retrieval."

The word "unmasking," which has a long and honorable history among histochemists, is a conspicuous improvement on "retrieval" because it says what happens. The epitopes of antigens were not retrieved (= brought back), because they were already there. The hot water and other chemicals made them accessible to the primary antibody by removing physical and chemical barriers ("masks") to the diffusion of large molecules.

BUT people are human and by nature conservative (= change can only make things worse), so it's likely that "retrieve" will win out over "unmask" despite any logical arguments. The HistoNet discussions ended when Biogenex said that the firm did not claim exclusive ownership of the "antigen retrieval" word pair, and we could say or write it without being sued.

John A. Kiernan, MB, ChB, PhD, DSc,
Department of Anatomy & Cell Biology,
The University of Western Ontario,
LONDON, Canada  N6A 5C1