Interferon-gamma (IFN-γ), also called type II interferon, is a homodimeric glycoprotein whose gene is located on chromosome 12. Unlike the synthesis of IFN-α and IFN-β, which can be of any cell, IFN-γ production is an exclusive function of T cells and NK cells. All IFN-γ inducers activate T cells, either in a polyclonal manner (mitogens or antibodies) or in a clone-limited, antigen-specific manner.
IFN-γ is produced during infection by cytotoxic/suppressor (CD8) T cells and by a subtype of helper T cells, Th1 cells. Th1 cells secrete IL-2, IL-3, TNF-β, and IFN-γ, whereas Th2 cells produce mainly IL-3, IL-4, IL-5, and IL-10, but little or no IFN-γ. IFN-γ preferentially inhibits the proliferation of Th2 cells but not Th1 cells, indicating that the presence of IFN-γ during an immune response will result in the selective proliferation of Th1 cells. IFN-γ is also produced by several different cell types under inflammatory conditions, including dendritic epidermal / γδ T-cells, keratinocytes, γδ peripheral blood T cells, mast cells, neurons, CD8+ T cells, neutrophils, NK cells, CD4+ T cells, and spermatids.
- IFN-γ is a potent activator of mononuclear phagocytes. For example, IFN-γ stimulates Mac-1 expression, increases monocyte endocytosis and phagocytosis, and activates macrophages to kill cancer cells, releasing reactive oxygen species and TNF-α.
- IFN-γ induces or enhances the expression of MHC antigens in macrophages, T- and B-cells, and in some cancerous cell lines.
- In T- and B-cells, IFN-γ promotes differentiation. It enhances the proliferation of activated B-cells and can act synergistically with IL-2 to increase the synthesis of immunoglobulin light chains. IFN-γ is one of the natural B-cell differentiation factors.
- Finally, IFN-γ activates neutrophils, NK cells, and vascular endothelial cells.
The role of IFN-γ as a biological marker has been demonstrated in several different pathological conditions:
Infections: IFN-γ is produced during viral infections. IFN-γ is a diagnostic tool for distinguishing tuberculous from other etiologies (non-tuberculous) ascites. IFN-γ values in the pleural fluid are significantly higher in patients with tuberculous pleurisy than in patients with non-tuberculous pleurisy, with sensitivity and specificity of almost 100%. The recurrence of clinical symptoms of erythema nodosum leprosum after treatment is associated with levels of IFN-γ and TNF-α.
Autoimmune diseases: Accurate measurements of cellular production of cytokines, such as IFN-γ, are essential in designing and monitoring multiple sclerosis immunotherapy.
Graft rejection: Within the graft, IFN-γ mRNA expression appears to be in acute graft rejection and precedes clinical graft rejection, thus providing an early diagnostic tool for detecting graft rejection.
Allergy: The production of IFN-γ by isolated lymphocytes is not detectable in patients with cow's milk allergy compared to normal subjects. Infants who develop atopy produce significantly less IFN-γ at birth than infants who do not develop atopy.
Diabetes: The peripheral blood cells of patients with type I diabetes produce significantly less IFN-γ compared to normal subjects and patients with long-term diabetes.
Important Note
Laboratory test results are the most critical parameter for diagnosing and monitoring all pathological conditions. Between 70 to 80% of diagnostic decisions are based on laboratory tests. Correctly interpreting laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be analyzed based on each case and family history, clinical findings, and the results of other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
