The ISG15 gene helps your cells respond to infection by adding a small signal tag to proteins and supporting interferon, one of the body’s main antiviral alarm systems. If this gene does not work properly, immune signaling can become unbalanced, which may raise the chance of certain infections, especially mycobacterial infections, and sometimes lead to inflammation. The ISG15 gene is mainly known in medicine through testing for rare immune conditions rather than through celebrity or media attention.
What is a gene?
A gene is a stretch of DNA that carries instructions your cells use to make molecules or regulate processes in the body. Some genes give the directions for building proteins, the functional parts of cells. Others mainly help manage when certain processes take place, where they happen, and how strongly they are active. Together, genes affect how the body grows and works, and they can influence how you respond to food, stress, or medications. To go into this topic in more detail, you can read more in the LearnHub.
Overview
ISG15Gene function
What if the gene works
The ISG15 gene helps cells respond to viral infection and fine tune immune signaling. It also tags certain proteins, which supports normal defense and inflammation control.
Risk
What if the gene does not work
Variants in the ISG15 gene can cause unusual susceptibility to mycobacterial infections and, in some people, excess interferon activity with brain calcifications. Milder or more severe variants may affect when problems begin and how strongly they appear.
Treatment
What does that mean for your treatment
No ISG15-specific treatment or drug-choice approach is currently established; care is guided by the person’s infections or inflammation rather than by a gene-targeted therapy. The ISG15 gene is also being studied as a biomarker and possible drug target in cancer and immune signaling research.
Conditions associated with ISG15
Gene function
What if the gene works
ISG15 helps your body respond to interferon, an immune alarm signal released during infections. When the ISG15 gene is active, cells can adjust early immune defenses in a coordinated way. Its main jobs include tagging certain proteins, supporting antiviral protection, and helping immune signals stay balanced.
ISG15 can attach a small tag to selected proteins during interferon responses. This tag can change how those proteins work, where they move, or how long they stay active.
Many cells make more ISG15 after interferon signals, especially during viral infections. This helps create an antiviral state, meaning cells are better prepared to slow viral growth. This is part of how the ISG15 gene helps fight viruses.
ISG15 can also act as a messenger outside cells. It helps natural killer cells and some T cells release interferon gamma, an immune signal that supports early defense.
In people, ISG15 helps keep interferon signaling well controlled by supporting USP18, a protein that acts like a brake. This allows a useful immune response to stay active without becoming overly prolonged.
What is a variant?
A genetic variant is a small 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 how the body responds to environmental influences. Many variants have no noticeable effect and simply represent natural genetic variation. In some cases, though, a variant can change how a gene functions more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
In discussions of how variants influence the ISG15 gene's function, most harmful changes reduce the amount of ISG15 made, make the protein unstable, or stop it from attaching to other proteins. Some variants also weaken its release from cells, which can disrupt interferon signaling, the body's antiviral alarm system. Milder variants may leave partial activity, while more severe variants can cause near-complete loss of function. That difference can shape how early and how strongly ISG15-related features appear.
How variants are linked to conditions
Pathogenic variants in the ISG15 gene can cause ISG15 deficiency, a rare inherited condition most often linked to Mendelian susceptibility to mycobacterial disease, meaning unusual illness after BCG vaccination or certain mycobacterial infections. In some people, ISG15 gene variants linked to conditions also include brain calcifications seen on scans, sometimes with neurologic symptoms. These associations are uncommon but well established in human genetics.
A variant is not necessarily a diagnosis
Variants in genes are a routine part of human biology and are widely present in the general population. Most do not have a direct effect on health and simply reflect natural human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definite diagnosis, especially when several genes and environmental factors are involved. In some situations, though, a single well characterized variant in a specific gene can be 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 health risk related to the ISG15 gene. For many living with a harmful ISG15 change, risk is shaped mainly by the variant itself rather than known lifestyle factors, so personal guidance from a doctor or genetic counselor can be helpful.
Inheritance of ISG15 variants
For families trying to understand how ISG15 gene variants are inherited, the well-established pattern is autosomal recessive. This means a child usually inherits one altered copy of the ISG15 gene from each parent. Parents who each carry one variant are often unaffected themselves, but with each pregnancy there is a 25% chance the child will inherit both variants, a 50% chance the child will be a carrier, and a 25% chance the child will inherit neither variant. Because the ISG15 gene is on chromosome 1, this pattern is the same for males and females.
What does my ISG15 result mean for my family?
For families with an ISG15-related condition, close relatives may also carry the gene change, and brothers or sisters could be affected or be carriers even if they feel well. Parents are often healthy carriers, and other relatives on both sides of the family may also carry the change. This can matter when relatives are planning children or when a family member has symptoms that fit the condition.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry an ISG15 variant, ISG15 genetic testing uses a blood or saliva sample to read the gene’s DNA and look for variants. Results can confirm a disease-causing variant, identify a harmless change, or find a variant of uncertain significance, which means the result is not yet clear.
When should I consider getting a genetic test?
Consider testing for changes in the ISG15 gene if you or your child has had unusual, severe infections after the BCG vaccine or from certain tuberculosis-like bacteria, especially if similar infections run in the family. Testing may also help when doctors suspect an inherited problem with the immune system.
A genetic result is only one part of your health story
Genetic results can be informative, but what they can tell you varies by the condition and the specific type of variant. Many other factors, including lifestyle, environment, age, and medical history, also shape how the body functions over time. In some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is most useful when considered alongside other parts of care. In other situations, a genetic result may give a clear answer. In areas like medication response, genetic results can also help put personal experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body handles certain medicines, so the same treatment may work differently from one person to another. Some people break down a drug more slowly or more quickly, while others are more or less sensitive to its effects. These inherited differences are common and can influence how well a medicine works or the chance of side effects. Medication response also reflects age, liver and kidney function, other medicines, and overall health.
What is Pharmacogenetics?
Pharmacogenetics explores how differences in genes can affect the way a person responds to medication. It examines connections between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes can influence how strongly a drug works or how the body processes it. This information can support treatment choices that are more informed and more personalized. To learn more about this topic, more information is available in the LearnHub.
Drugs influenced by the ISG15 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding how medicines are chosen or adjusted, so any concerns about treatment, side effects, or drug interactions are best discussed with your doctor or pharmacist.
History
The ISG15 gene entered medical research in the late 1970s, when scientists studying the body’s response to interferon noticed a small protein that became highly active during viral infection. In 1987, researchers identified the matching gene and gave it the name ISG15, short for “interferon stimulated gene 15.” From these first observations, research expanded steadily. During the 1990s and 2000s, the ISG15 gene drew interest as part of a broader effort to map how immune signals are switched on and off. A major clinical milestone came in 2012, when inherited variants in the ISG15 gene were linked to a rare vulnerability to certain infections, especially mycobacterial disease. That finding connected years of laboratory work with a clear human health condition.