interferon-gamma release assay
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Interferon-γ release assays (IGRA) are medical tests used in the diagnosis of some infectious diseases, especially
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, i ...
.
Interferon-γ Interferon gamma (IFN-γ) is a dimerized soluble cytokine 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 ...
(IFN-γ) release assays rely on the fact that T-lymphocytes will release IFN-γ when exposed to specific antigens. These tests are mostly developed for the field of
tuberculosis diagnosis Tuberculosis is diagnosed by finding '' Mycobacterium tuberculosis'' bacteria in a clinical specimen taken from the patient. While other investigations may strongly suggest tuberculosis as the diagnosis, they cannot confirm it. A complete medica ...
, but in theory, may be used in the diagnosis of other diseases which rely on cell-mediated immunity, e.g. cytomegalovirus and leishmaniasis. For example, in patients with
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different d ...
adverse drug reaction An adverse drug reaction (ADR) is a harmful, unintended result caused by taking medication. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs. The meaning of this term ...
s, challenge of peripheral blood lymphocytes with the drug causing the reaction produced a positive test result for half of the drugs tested. There are currently two IFN-γ release assays available for the diagnosis of tuberculosis: * QuantiFERON-TB Gold (licensed in US, Europe and Japan); and * T-SPOT.TB, a form of
ELISpot The enzyme-linked immune absorbent spot (ELISpot) is a type of assay that focuses on quantitatively measuring the frequency of cytokine secretion for a single cell. The ELISpot Assay is also a form of immunostaining since it is classified as a tec ...
, the variant of
ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presen ...
(licensed in Europe, US, Japan and China). The former test quantitates the amount of
IFN-γ Interferon gamma (IFN-γ) is a dimerized soluble cytokine 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 ...
produced in response to the ESAT-6 and CFP-10 antigens from ''Mycobacterium tuberculosis'', which are distinguishable from those present in BCG and most other non-tuberculous mycobacteria. The latter test determines the total number of individual effector T cells expressing
IFN-γ Interferon gamma (IFN-γ) is a dimerized soluble cytokine 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 ...
. The indications for the test are still disputed. It has been evaluated for the diagnosis of latent tuberculosis in HIV patients (who frequently have a negative
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 ...
).


References

{{Tuberculosis Tuberculosis