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 a number of 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, e.g. IFN-γ stimulates Mac-1 expression, increases endocytosis and phagocytosis by monocytes, 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 a number of 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, e.g. of IFN-γ, are important in the design and monitoring of 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.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of 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 interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal 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 we contact your doctor to get the best possible medical care.