[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Immunology](https://durgical.com/en/immunology/) › [Cytokines and molecules](https://durgical.com/en/immunology/#a-molecules) › Interferon-γ [Immunology](https://durgical.com/en/immunology/) · [Cytokines and molecules](https://durgical.com/en/immunology/#a-molecules) # Interferon-γ - Molecule Interferon-γ is the signal that turns macrophages into killers. It is what the blood test for latent tuberculosis (IGRA) measures. Updated 2026-11-01 ## Key points - Sources: Th1, CD8 T cells, NK cells; induced by IL-12. - Activates macrophages: phagolysosome fusion, reactive oxygen and nitrogen species (iNOS), autophagy. - Raises MHC class I and II expression and promotes Th1 while inhibiting Th2. - IGRA tests measure IFN-γ released by T cells exposed to ESAT-6 and CFP-10 (absent from BCG). - Defects in IFN-γ production or response: Mendelian susceptibility to mycobacterial disease. - Recombinant IFN-γ-1b reduces serious infections in chronic granulomatous disease. ## What it is Interferon-γ, the only type II interferon, is made by Th1 cells, CD8 T cells, NK cells and group 1 innate lymphoid cells, mostly in response to IL-12. It binds the IFN-γ receptor (IFNGR1/IFNGR2) and signals through JAK1, JAK2 and STAT1. Its main job is to activate macrophages so they can kill intracellular microbes such as Mycobacterium tuberculosis. ## Function - Macrophage activation (classical, M1) and granuloma integrity. - Better antigen presentation through more MHC class I and II. - Stimulates IL-12 production, closing a positive loop with Th1 cells. ## Clinical notes - Tuberculosis and tuberculoid leprosy: a strong Th1/IFN-γ response contains the bacilli; in lepromatous leprosy the response is weak. - IFN-γ receptor, IL12RB1 or STAT1 defects: severe infections with BCG, nontuberculous mycobacteria and Salmonella. - Chronic granulomatous disease: recombinant IFN-γ-1b lowers the frequency and severity of serious infections. ## In the lab - IGRA: blood is exposed to M. tuberculosis antigens and IFN-γ release is measured; BCG vaccination does not cause false positives. - IGRA is preferred over the skin test in BCG-vaccinated people (as most people in Colombia are). - Neither IGRA nor the skin test separates latent from active tuberculosis; that requires clinical evaluation, chest X-ray and sputum tests. ## Memory aid Gamma is the general who arms the macrophage: without its order the soldier swallows the bacillus but cannot kill it. ## Test yourself Think of the answer, then tap the question to see it. ## Why is an IGRA not affected by BCG vaccination? It uses ESAT-6 and CFP-10, antigens present in M. tuberculosis but absent from BCG vaccine strains. ## Which cytokine induces IFN-γ production by Th1 and NK cells? IL-12 from dendritic cells and macrophages. ## Can a positive IGRA tell latent from active tuberculosis? No; it only shows sensitisation to M. tuberculosis. Symptoms, chest X-ray and sputum studies are needed. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/immunology/interferon/) ## Related - [Cytokines: the table to know](https://durgical.com/en/immunology/cytokines-the-table-to-know/) - [IL-12 and IL-23](https://durgical.com/en/immunology/il-12-and-il-23/) - [TNF-α](https://durgical.com/en/immunology/tnf/) - [Type I interferons (α, β)](https://durgical.com/en/immunology/type-i-interferons/) - [IL-4, IL-5 and IL-13 (the Th2 cytokines)](https://durgical.com/en/immunology/il-4-il-5-and-il-13/) - [Tuberculin skin test and IGRA](https://durgical.com/en/immunology/tuberculin-skin-test-and-igra/) - [Monocyte and macrophage](https://durgical.com/en/immunology/monocyte-and-macrophage/) - [Granulomatous inflammation](https://durgical.com/en/immunology/granulomatous-inflammation/) - [Th1, Th2, Th17, Tfh and Treg](https://durgical.com/en/immunology/th1-th2-th17-tfh-and-treg/) - [Phagocyte defects: CGD, LAD, Chédiak–Higashi](https://durgical.com/en/immunology/phagocyte-defects-cgd-lad-chediak-higashi/) - [Natural killer cell](https://durgical.com/en/immunology/natural-killer-cell/) ## Related conditions - [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/) - [Pulmonary tuberculosis](https://durgical.com/en/conditions/pulmonary-tuberculosis/) ## Microorganisms - [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/) - [Mycobacterium leprae](https://durgical.com/en/microbiology/mycobacterium-leprae/) - [Non-typhoidal Salmonella](https://durgical.com/en/microbiology/non-typhoidal-salmonella/) [← All of immunology](https://durgical.com/en/immunology/) Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given. Sources: [IFN-γ-Driven macrophage responses in the immunity to Mycobacterium tuberculosis and Mycobacterium leprae](https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2025.1679691/full) (Frontiers in Cellular and Infection Microbiology, 2025); [Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection --- United States, 2010](https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5905a1.htm) (CDC, MMWR Recommendations and Reports, 2010); [Overview of Mendelian Susceptibility to Mycobacterial Diseases (MSMD)](https://pmc.ncbi.nlm.nih.gov/articles/PMC12255513/) (Cureus (PubMed Central), 2025); [The Dual Nature of Type I and Type II Interferons](https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2018.02061/full) (Frontiers in Immunology, 2018). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/immunology/interferon/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/interferon/