The IL12B gene helps make an immune system signal that lets white blood cells coordinate their response to infection. This gene plays an important role in helping your body control certain bacteria and keep inflammation balanced. If it does not work properly, some people can have a rare inherited condition with repeated infections, especially from mycobacteria, a group of germs that includes the one linked to tuberculosis, and from Salmonella. Other variants in the IL12B gene may influence the chance of conditions such as psoriasis or inflammatory bowel disease.
What is a gene?
Genes are stretches of DNA that hold instructions your cells use either to make molecules or to regulate processes in the body. Some genes provide the directions for producing proteins, which are the working parts of cells. Others mainly control when certain processes happen, where they take place, and how strongly they operate. Taken together, genes affect how the body develops and works, and they can also shape your response to food, stress, or medications. To go further into this subject, you can learn more in the LearnHub.
Overview
IL12BGene function
What if the gene works
The IL12B gene helps immune cells send signals that guide inflammation and defense against germs. Its protein is part of signals that help certain white blood cells respond to infection.
Risk
What if the gene does not work
Reduced function of the IL12B gene is linked to Mendelian susceptibility to mycobacterial disease, often causing unusual or repeated mycobacterial infections and Salmonella infections. Milder or more severe variants can change when symptoms begin, how severe they are, and which infections appear.
Treatment
What does that mean for your treatment
Pathogenic loss-of-function variants in the IL12B gene can guide care toward prolonged treatment of mycobacterial or Salmonella infections, often with several antibiotics. Recombinant interferon gamma can also help some people by supporting the immune signal that is reduced, while stem cell transplant is not routine for most.
Conditions associated with IL12B
Gene function
What if the gene works
Your immune system depends on clear signals so white blood cells can work together. The IL12B gene helps make one of these key signals when your body meets everyday germs. This helps explain how the IL12B gene supports immune signaling during routine immune defense.
The IL12B gene provides a protein piece used to build two immune messengers, called IL-12 and IL-23. Sharing this piece helps different immune pathways connect and coordinate their response.
As part of IL-12, this gene helps white blood cells activate a more targeted defense. It supports natural killer cells and T cells as they respond to viruses, some bacteria, and other invading germs.
As part of IL-23, the IL12B gene supports immune cells that help guard the skin, gut, and other body linings. This helps your body maintain a controlled response where germs commonly enter.
What is a variant?
A genetic variant is a slight change in the DNA sequence within a gene. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, or the way the body responds to environmental influences. Many variants do not cause any noticeable effect and simply represent natural genetic variation. In some situations, though, a variant can change how a gene works more significantly and may contribute to or directly cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the IL12B gene can lower or disrupt production of the p40 protein, so immune cells send weaker IL-12 and IL-23 signals. This helps explain how IL12B gene variants affect immune signaling at a cellular level. Milder variants may leave some protein activity, while more severe variants can stop protein release or make it unstable, causing a larger functional drop. In people with IL12B deficiency, that often tracks with earlier or more noticeable trouble fighting infections.
How variants are linked to conditions
Pathogenic variants in the IL12B gene can cause a rare inherited immune condition called Mendelian susceptibility to mycobacterial disease, where people are more prone to infections from BCG vaccine strains, environmental mycobacteria, and sometimes Salmonella. Other variants in the IL12B gene are linked to a higher risk of psoriasis and some inflammatory bowel diseases, but these common risk variants do not mean a person will develop those conditions.
A variant is not necessarily a diagnosis
Genetic variants are a routine feature of human biology and are widely found across the general population. Most do not directly affect health and simply contribute to normal human variation. For many genes, having a variant associated with a condition points to a possible link, not a certain diagnosis, particularly when several genes and environmental influences play a role. In some situations, though, one clearly established variant in a particular gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
There is not yet broadly confirmed evidence on specific factors that clearly increase or reduce risk related to IL12B itself. Overall risk can vary depending on the exact gene change, family history, and immune health, so people with questions about their personal risk should speak with a doctor or genetic counselor.
Inheritance of IL12B variants
For the rare immune condition linked to harmful changes in the IL12B gene, IL12B gene inheritance follows an autosomal recessive pattern. This means a child usually inherits one altered copy from each parent. When both parents carry one altered copy, each pregnancy has a 25% chance of the child inheriting both altered copies, a 50% chance of being a carrier, and a 25% chance of inheriting neither altered copy. Parents who are carriers usually do not have the condition themselves.
What does my IL12B result mean for my family?
For IL12B, family meaning is usually discussed in the setting of a rare immune condition that is passed down in a recessive way. This often means parents are healthy carriers, brothers or sisters could also be affected or be carriers, and other close relatives may carry the same change. Knowing the exact IL12B result can help clarify which relatives might want to discuss testing.
Genetic information
Genetic testing
How you find out about variants
To look for changes in the IL12B gene, doctors use genetic testing for IL12B variants on a blood sample, saliva, or a cheek swab. A lab reads the DNA code and checks for variants linked to immune system conditions. Results can show whether a variant is present, absent, or of uncertain significance.
When should I consider getting a genetic test?
You might consider IL12B testing if you or your child has had repeated or unusually severe infections from TB-like bacteria, illness after the BCG vaccine, or serious salmonella infections. Testing can also make sense when these infections run in the family or start early in life.
A genetic result is only one part of your health story
Genetic results can be informative, but how much they reveal varies by the condition and the type of variant involved. Over time, factors such as lifestyle, environment, age, and medical history also shape how the body functions. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is best considered alongside other parts of care. In other situations, a genetic result can provide a clear answer. In areas like medication response, genetic results may also help explain individual experiences.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in genes can change how the body breaks down a drug, moves it through the body, or responds to it at its target. This is common and can help explain why the same treatment works well for one person, works less well for another, or causes more side effects in some people.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in a person’s genes affect the way they respond to medicines. By studying the relationship between genes and drugs, it helps explain why the same treatment can work differently from one person to another. For many medicines, genes influence both how strongly a drug works and how the body processes it. This information can support treatment decisions that are more informed and more individualized. More detail on this topic is available in the LearnHub.
Drugs influenced by the IL12B gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding how medicines are used, so questions about side effects, treatment changes, or general health are best discussed with your doctor. IL12B has been studied in research on response to some immune-targeting treatments, but these findings are not used routinely in everyday care.
History
In the early 1990s, researchers identified the IL12B gene while studying immune signaling molecules that help the body respond to infection. Early work linked IL12B to interleukin 12, and this helped shape a growing field of cytokine research. Building on this early work, scientists later recognized that the same gene also contributes to interleukin 23, which changed how several inflammatory conditions were understood. That shift was especially important in psoriasis research, where IL12B became part of the story behind newer targeted treatments. Scientific classifications changed as researchers learned more about the gene. Today, the history of the IL12B gene is closely tied to major advances in modern immunology and inflammation research.