[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) › IL-12 and IL-23 [Immunology](https://durgical.com/en/immunology/) · [Cytokines and molecules](https://durgical.com/en/immunology/#a-molecules) # IL-12 and IL-23 - Molecule IL-12 and IL-23 are sister cytokines from dendritic cells and macrophages: IL-12 creates Th1 cells and IL-23 keeps Th17 cells going. Updated 2026-11-01 ## Key points - Shared p40 subunit: ustekinumab blocks p40, so it blocks both IL-12 and IL-23. - IL-23 = p19 + p40; p19-specific antibodies (guselkumab, risankizumab, tildrakizumab) block only IL-23. - IL-12 → Th1 → IFN-γ → macrophage killing of intracellular microbes. - IL-23 → Th17 survival and expansion → IL-17. - Inherited IL-12/IFN-γ axis defects (IL12RB1, IL12B): disseminated BCG, nontuberculous mycobacteria, Salmonella. ## What it is IL-12 and IL-23 share one subunit, p40; IL-12 adds p35 and IL-23 adds p19. Both are made by dendritic cells and macrophages after they sense microbes through Toll-like and other receptors. IL-12 drives Th1 cells and IFN-γ (key against mycobacteria and Salmonella), whereas IL-23 sustains Th17 cells and IL-17 (key in psoriasis and inflammatory bowel disease). ## Step by step - Dendritic cells and macrophages detect a microbe (for example a mycobacterium). - They secrete IL-12 (p35+p40) and IL-23 (p19+p40). - IL-12 binds IL-12Rβ1/β2 on naive CD4 T and NK cells → Th1 differentiation and IFN-γ. - IFN-γ activates macrophages, which make more IL-12: a positive loop. - IL-23 binds IL-23R/IL-12Rβ1 on Th17 cells and keeps them producing IL-17. ## Clinical notes - Psoriasis and psoriatic arthritis: ustekinumab and anti-p19 antibodies. - Crohn disease and ulcerative colitis: ustekinumab and anti-IL-23 antibodies (guselkumab, risankizumab, mirikizumab). - Mendelian susceptibility to mycobacterial disease: IL12RB1 deficiency is the most common genetic cause; disseminated BCG after vaccination is often the first sign. - These drugs increase the risk of tuberculosis: latent tuberculosis is screened for before treatment. ## Memory aid Twelve and twenty-three share the same p40 heart: twelve gives life to Th1, twenty-three keeps Th17 alive. ## Test yourself Think of the answer, then tap the question to see it. ## Which subunit do IL-12 and IL-23 share? p40; IL-12 also has p35 and IL-23 has p19. ## Why does ustekinumab block both IL-12 and IL-23? It targets the shared p40 subunit, whereas anti-p19 antibodies block only IL-23. ## An infant develops disseminated infection after BCG vaccination. Which cytokine axis is suspected? The IL-12/IFN-γ axis (for example IL12RB1 or IFN-γ receptor deficiency), known as Mendelian susceptibility to mycobacterial disease. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/immunology/il-12-and-il-23/) ## Related - [Cytokines: the table to know](https://durgical.com/en/immunology/cytokines-the-table-to-know/) - [Interferon-γ](https://durgical.com/en/immunology/interferon/) - [Interleukin-17](https://durgical.com/en/immunology/interleukin-17/) - [IL-10 and TGF-β (the brakes)](https://durgical.com/en/immunology/il-10-and-tgf/) - [Th1, Th2, Th17, Tfh and Treg](https://durgical.com/en/immunology/th1-th2-th17-tfh-and-treg/) - [Dendritic cell (professional antigen-presenting cell)](https://durgical.com/en/immunology/dendritic-cell/) - [Granulomatous inflammation](https://durgical.com/en/immunology/granulomatous-inflammation/) - [Phagocyte defects: CGD, LAD, Chédiak–Higashi](https://durgical.com/en/immunology/phagocyte-defects-cgd-lad-chediak-higashi/) ## Related conditions - [Crohn disease](https://durgical.com/en/conditions/crohn-disease/) - [Ulcerative colitis](https://durgical.com/en/conditions/ulcerative-colitis/) - [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/) ## Microorganisms - [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/) - [Non-typhoidal Salmonella](https://durgical.com/en/microbiology/non-typhoidal-salmonella/) ## In Pharmacology - [Ustekinumab](https://durgical.com/en/pharmacology/ustekinumab/) [← 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: [Major Role of the IL17/23 Axis in Psoriasis Supports the Development of New Targeted Therapies](https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.621956/full) (Frontiers in Immunology, 2021); [Overview of Mendelian Susceptibility to Mycobacterial Diseases (MSMD)](https://pmc.ncbi.nlm.nih.gov/articles/PMC12255513/) (Cureus (PubMed Central), 2025); [Ustekinumab Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a611013.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [Th17/Treg imbalance in inflammatory bowel disease: immunological mechanisms and microbiota-driven regulation](https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2025.1651063/full) (Frontiers in Immunology, 2025). ## **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/il-12-and-il-23/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/il-12-and-il-23/