Gliotoxin: The Immunosuppressive Mycotoxin That May Indicate Colonisation
Gliotoxin is an immunosuppressive mycotoxin produced principally by Aspergillus fumigatus. It disables the oxidative burst that neutrophils use to kill invading organisms, which is why it functions as a virulence factor during infection. A positive result raises a question the other mycotoxins do not: whether the fungus is growing in the body rather than only in the building.
Both dietary and building-associated
Gliotoxin is unusual on a mycotoxin panel because it can be produced in situ. Aspergillus colonising a sinus or airway generates it internally, so a result may reflect carriage rather than environmental exposure.
Which fungi produce gliotoxin
The principal producer and the species most associated with human colonisation and invasive disease.
Several produce gliotoxin in smaller quantities, including strains found on damp indoor materials.
Reported as a producer, which is why gliotoxin is sometimes raised in the context of yeast overgrowth rather than mold exposure.
Some species produce gliotoxin and are found on wet building materials.
Where exposure comes from
A urine panel confirms that a compound reached you. It cannot say by which route. These are the realistic possibilities, which is what a result has to be read against.
Aspergillus growing in the respiratory tract produces gliotoxin continuously, independent of current environmental exposure.
Aspergillus fumigatus grows readily on damp materials and in air handling systems, particularly where warmth and humidity are constant.
Aspergillus fumigatus is thermotolerant and abundant in composting material, which is a recognised occupational exposure.
Candida-derived gliotoxin has been reported, linking a positive result to intestinal rather than environmental sources in some cases.
How it affects the body
Gliotoxin belongs to the epipolythiodioxopiperazine class, defined by an internal disulfide bridge. That bridge is the toxic element: it undergoes redox cycling that generates reactive oxygen species, and it forms mixed disulfides with cysteine residues on proteins, disabling them.
Its most consequential target is NADPH oxidase. By preventing assembly of that enzyme complex, gliotoxin blocks the respiratory burst neutrophils depend on to kill phagocytosed fungi, which is precisely how it protects the organism producing it.
It also induces apoptosis in macrophages, dendritic cells and T lymphocytes, and interferes with NF-kB signalling. The combined effect is broad suppression of exactly the cells that would otherwise clear an Aspergillus infection.
Documented health effects
The defining effect. Neutrophil function, macrophage survival and T cell responses are all impaired, which is why gliotoxin is studied as a virulence factor in invasive aspergillosis.
Redox cycling generates oxidative stress and the disulfide bridge modifies protein thiols directly, damaging cells independently of the immune effects.
DNA damage is documented in laboratory systems, attributed to the reactive oxygen species generated during redox cycling.
How it is measured
Measured in urine on multi-mycotoxin panels by mass spectrometry or immunoassay. Gliotoxin is chemically less stable than ochratoxin A, which makes sample handling and analytical method more consequential for the result.
Where colonisation is suspected rather than environmental exposure, the useful follow-up is clinical rather than analytical: imaging or culture of the sinuses and airway answers a question a urine panel cannot.
The wider question of what these panels can and cannot establish is covered in the guide to mycotoxin urine testing.
Reading a gliotoxin result
Treat a gliotoxin result as a question about location as much as quantity. Because Aspergillus can produce it inside the body, a positive finding does not distinguish between a colonised sinus and a contaminated building, and those two situations call for entirely different responses.
The distinction matters practically. Remediating a house will not resolve gliotoxin originating from an airway colony, and antifungal treatment will not resolve exposure from a building that is still wet.
Read the result alongside the rest of the panel. Gliotoxin with macrocyclic trichothecenes suggests a shared environmental source. Gliotoxin alone, particularly with sinus symptoms, points more toward colonisation and is worth raising with a clinician.
If you are holding a panel and want each value explained, the free lab report interpreter reads mycotoxin results alongside ERMI and HERTSMI-2 building scores and the inflammatory markers used in biotoxin illness, and explains what each one indicates.
Frequently asked questions
What does a positive gliotoxin result mean?
It indicates exposure to gliotoxin-producing fungi, principally Aspergillus fumigatus. Unlike most mycotoxins it can be produced inside the body by fungus colonising a sinus or airway, so a positive result does not distinguish between environmental exposure and colonisation. That distinction changes what you should do next.
Why is gliotoxin described as immunosuppressive?
It blocks NADPH oxidase, the enzyme neutrophils use to generate the oxidative burst that kills engulfed organisms, and it induces apoptosis in macrophages and T cells. The net effect is suppression of the immune cells that would otherwise clear an Aspergillus infection, which is why it functions as a virulence factor.
Can Candida produce gliotoxin?
Candida albicans has been reported as a producer, which is why gliotoxin sometimes appears in the context of suspected yeast overgrowth rather than mold exposure. It is one reason a gliotoxin result should be interpreted alongside clinical findings rather than in isolation.
Does remediating my home fix a gliotoxin result?
Only if the source is the building. If Aspergillus is colonising a sinus or airway, it will keep producing gliotoxin regardless of the state of the house. That is why the practical next step is usually a clinical assessment rather than more environmental testing.
Screening for Biotoxin Effects
A mycotoxin result describes what your body is clearing. The Visual Contrast Sensitivity test measures something different, a neurological effect associated with biotoxin exposure, which gives a second and independent data point. Free, in your browser, about 15 minutes.