Interferon gamma (IFN-γ) is a
dimer
Dimer may refer to:
* Dimer (chemistry), a chemical structure formed from two similar sub-units
** Protein dimer, a protein quaternary structure
** d-dimer
* Dimer model, an item in statistical mechanics, based on ''domino tiling''
* Julius Dimer ( ...
ized soluble
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in au ...
that is the only member of the type II class of
interferon
Interferons (IFNs, ) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten th ...
s.
The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheelock as a product of human
leukocyte
White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...
s stimulated with
phytohemagglutinin, and by others as a product of antigen-stimulated
lymphocytes
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic ada ...
.
It was also shown to be produced in human lymphocytes. or
tuberculin
Tuberculin, also known as purified protein derivative, is a combination of proteins that are used in the diagnosis of tuberculosis. This use is referred to as the tuberculin skin test and is recommended only for those at high risk. Reliable admi ...
-sensitized mouse
peritoneal
The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mes ...
lymphocytes challenged with
Mantoux test
The Mantoux test or Mendel–Mantoux test (also known as the Mantoux screening test, tuberculin sensitivity test, Pirquet test, or PPD test for purified protein derivative) is a tool for screening for tuberculosis (TB) and for tuberculosis diagn ...
(PPD); the resulting
supernatant
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
s were shown to inhibit growth of
vesicular stomatitis virus
''Indiana vesiculovirus'', formerly ''Vesicular stomatitis Indiana virus'' (VSIV or VSV) is a virus in the family '' Rhabdoviridae''; the well-known '' Rabies lyssavirus'' belongs to the same family. VSIV can infect insects, cattle, horses and pi ...
. Those reports also contained the basic observation underlying the now widely employed
IFN-γ release assay used to test for
tuberculosis
Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, ...
. In humans, the IFN-γ protein is encoded by the ''IFNG''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
Through cell signaling, IFN-γ plays a role in regulating the immune response of its target cell.
A key signaling pathway that is activated by type II IFN is the
JAK-STAT signaling pathway
The JAK-STAT signaling pathway is a chain of interactions between proteins in a cell, and is involved in processes such as immunity, cell division, cell death, and tumour formation. The pathway communicates information from chemical signals ou ...
.
IFN-γ plays an important role in both