The AIRE gene, or Autoimmune Regulator, is an important part of the human immune system. Located on chromosome 21, this gene provides instructions for making the autoimmune regulator protein. This protein plays a key role in preventing the immune system from mistakenly attacking the body’s own tissues.
The Immune System’s Self-Defense Mechanism
The human immune system protects the body from harmful invaders like bacteria, viruses, and fungi. It does this by distinguishing between “self” (the body’s own cells and tissues) and “non-self” (foreign substances). This distinction, called self-tolerance, prevents the immune system from attacking the body itself. If this system malfunctions, it can mistakenly target healthy cells, leading to autoimmune diseases.
The thymus, an organ behind the breastbone, trains T-cells. Here, developing T-cells learn to differentiate between self and non-self. This process ensures that only T-cells that can target foreign threats without harming the body’s own tissues mature and circulate.
How AIRE Teaches the Immune System
The AIRE gene provides instructions for producing the autoimmune regulator protein, which functions as a transcription factor. This means the AIRE protein controls the activity of other genes by regulating their transcription into RNA. In the thymus, AIRE is active primarily in medullary thymic epithelial cells, where it drives the expression of various “tissue-specific antigens” (TSAs).
These TSAs are proteins normally found in other organs, such as insulin from the pancreas or thyroid proteins. AIRE induces their expression in the thymus, a process called “ectopic expression.” This allows developing T-cells to encounter these self-antigens during maturation. T-cells that react too strongly to these self-antigens are then “negatively selected,” meaning they are either deleted or inactivated.
The Consequences of AIRE Dysfunction
When the AIRE gene is mutated, the process of self-tolerance can break down. This malfunction leads to Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APS-1), also known as Autoimmune Polyendocrine Syndrome Type 1 or APECED. In individuals with a faulty AIRE gene, self-reactive T-cells, normally eliminated in the thymus, escape into circulation. These rogue T-cells then attack various organs and tissues, leading to a range of autoimmune manifestations.
APS-1 is characterized by symptoms affecting multiple endocrine glands and other tissues. Common manifestations include chronic mucocutaneous candidiasis (CMC), persistent fungal infections of the skin, nails, and mucous membranes, often caused by Candida. Endocrine deficiencies are also prevalent, such as hypoparathyroidism (low calcium) and adrenal insufficiency (affecting hormone production). Individuals may also experience hypogonadism, Type 1 diabetes, or thyroid disease. The specific combination and severity of symptoms vary significantly.
Living with AIRE-Related Conditions
Diagnosis of APS-1 involves clinical presentation and genetic testing to identify AIRE gene mutations. Observing the characteristic cluster of symptoms, especially chronic mucocutaneous candidiasis alongside endocrine issues, prompts suspicion. Genetic testing confirms the diagnosis by revealing specific mutations in the AIRE gene. These mutations can result in an abnormally short or non-functional autoimmune regulator protein.
Management of APS-1 is symptomatic, focusing on replacing deficient hormones and treating infections. For example, hypoparathyroidism is managed with calcium and vitamin D supplementation, and adrenal insufficiency requires lifelong corticosteroid replacement therapy. Chronic candidiasis is treated with antifungal medications. Individuals with APS-1 require lifelong monitoring and a multidisciplinary approach to care, involving specialists like endocrinologists, immunologists, and dermatologists. While current treatments address symptoms, ongoing research aims to develop more targeted therapies or potential cures.