Interferon gamma (IFNG or IFN-γ) is a
dimerized soluble
cytokine
Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling.
Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...
that is the only member of the type II class of
interferons.
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
leukocytes 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 T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), and ...
.
It was also shown to be produced in human lymphocytes. or
tuberculin-sensitized mouse
peritoneal lymphocytes challenged with
Mantoux test (PPD); the resulting
supernatants were shown to inhibit growth of
vesicular stomatitis virus. Those reports also contained the basic observation underlying the now widely employed
interferon gamma release assay used to test for
tuberculosis
Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...
. In humans, the IFNG protein is encoded by the ''IFNG''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Through cell signaling, interferon gamma 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.
IFNG plays an important role in both