Immunohistochemistry vs Immunocytochemistry

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People often confuse the terms immunohistochemistry, immunocytochemistry, and immunofluorescence. These terms should not be used interchangeably for any method of immunostaining.

I’ve outlined the key differences so you don’t make a newbie mistake by using the wrong term in an abstract or presentation. Let’s start by breaking down these terms into their prefixes, roots, and suffixes.

ROOT WORD MEANINGS:

For the most part, the terms immunohistochemistry and immunocytochemistry are used correctly for their broad meaning to “use an antibody to detect an antigen” in a tissue or cell, respectively.

The problem arises when people use a fluorophore to detect the primary antibody, either through a direct conjugation to the primary antibody or through a labelled secondary antibody.

This technique is then labelled as immunofluorescence. This term only reveals the detection method that was used, not the sample type.

Biotech companies often designate their primary antibodies as being tested for use in immunofluorescence. What does this tell you? Not much.

If you are trying to choose a product based on whether they have been validated for use in particular application, the most important consideration is whether it has been validated in your sample type (ie. tissue or cells), not the detection system (-chemistry or -fluorescence).

This is why I find immunofluorescence as an application term for primary antibodies to be especially useless.

In a perfect world I would love to see “-chemistry” replaced with “-fluorescence” at the end of each term when necessary. This would indicate which visualization method was used, while keeping the sample type information.

Proposed Nomenclature for Immunostaining Techniques

IMMUNOCHEMISTRY (IC) DEFINITION

Detection of a target using an antibody and subsequent visualization using a chemical reaction to produce a color change.

Immunohistochemistry (IHC) Definition

Detection of a target in tissue using an antibody and subsequent visualization using a chemical reaction to produce a color change.

Immunocytochemistry (ICC) Definition

Detection of a target in cells using an antibody and subsequent visualization using a chemical reaction to produce a color change.

IMMUNOFLUORESCENCE (IF) DEFINITION

Detection of a target using an antibody and subsequent visualization using a fluorophore

Immunohistofluorescence (IHF) Definition

Detection of a target in tissue using an antibody and subsequent visualization using a fluorophore

Immunocytofluorescence (ICF) Definition

Detection of a target in cells using an antibody and subsequent visualization using a fluorophore

I didn’t coin these terms, but checking the google search volumes for each of them clearly shows that there is a long road ahead of us if we want these terms to take over as the norm.

Since immunofluorescence (IF) as a term is still widely used, we caved to peer pressure and grouped it in with our immunocytochemistry (ICC) application term, as those two techniques are often combined.

This results in the ICC/IF abbreviation that you will see used throughout our website.

Any antibody labeled as being tested for use in ICC/IF has been validated using cells with a secondary antibody conjugated to either a fluorescent or enzyme/protein tag.

If you see the abbreviation for immunohistochemistry (IHC), it means that the antibody can be used in tissue with a secondary antibody conjugated to any tag, as that does not affect the binding of the primary antibody.

Looking for more information on IHC and ICC protocols and techniques? We will have subsequent blogs on these applications in the coming weeks. Stay tuned!