Nitro blue tetrazolium is a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 composed of two tetrazole

Tetrazole

Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen and one carbon atom . The simplest is tetrazole itself, CN4H2. They are unknown in nature...

 moieties. It is used in immunology

Immunology

Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

 for sensitive detection of alkaline phosphatase

Alkaline phosphatase

Alkaline phosphatase is a hydrolase enzyme responsible for removing phosphate groups from many types of molecules, including nucleotides, proteins, and alkaloids. The process of removing the phosphate group is called dephosphorylation...

 (with BCIP). NBT serves as the oxidant and BCIP is the AP-substrate

Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...

 (and gives also dark blue dye).

Clinical significance

In immunohistochemistry

Immunohistochemistry

Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...

 the alkaline phosphatase is often used as a marker, conjugated to an antibody

Antibody

An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

. The colored product can either be of the NBT/BCIP reaction reveals where the antibody is bound, or can be used in immunofluorescence

Immunofluorescence

Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on biological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows...

.

The NBT/BCIP reaction is also used for colorimetric/spectrophotometric

Spectrophotometry

In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength...

 activity assays

Enzyme assay

Enzyme assays are laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition.-Enzyme units:...

 of oxidoreductase

Oxidoreductase

In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another...

s. One application is in activity stains in gel electrophoresis

Gel electrophoresis

Gel electrophoresis is a method used in clinical chemistry to separate proteins by charge and or size and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge...

, such as with the mitochondrial electron transport chain

Electron transport chain

An electron transport chain couples electron transfer between an electron donor and an electron acceptor with the transfer of H+ ions across a membrane. The resulting electrochemical proton gradient is used to generate chemical energy in the form of adenosine triphosphate...

 complexes.

Nitro blue tetrazolium is used in a diagnostic test, particularly for chronic granulomatous disease

Chronic granulomatous disease

Chronic granulomatous disease is a diverse group of hereditary diseases in which certain cells of the immune system have difficulty forming the reactive oxygen compounds used to kill certain ingested pathogens...

 and other diseases of phagocyte function. A disease where there is a defect in NADPH oxidase

NADPH oxidase

The NADPH oxidase is a membrane-bound enzyme complex. It can be found in the plasma membrane as well as in the membrane of phagosome.-Subunits:It is made up of six subunits...

, therefore the phagocyte is unable to make the reactive oxygen species or radicals required for bacterial killing and results in bacteria thriving within the phagocyte. The higher the blue score, the better the cell is at producing reactive oxygen species.