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Superantigens (SAgs) are a group of virulent toxins that indiscriminately activate T-cells of the immune system causing system-wide inflammation and other serious, potentially fatal symptoms. They are not quite the same as antigens, though they almost all have antigenic properties, but rather receive their name from their powers to induce the production of antibodies.
Symptoms
Characteristic symptoms of superantigen-mediated diseases include:
Chronic infection can cause autoimmune diseases and glomerulonephritis.
Pathophysiology
Superantigens are secreted as exotoxins by bacteria, alternatively viruses hijack our own molecular machinery to generate endotoxin forms of superantigens. They are mainly associated with species of Streptococcus and Staphylococcus infections, and are the contributing cause of toxic shock syndrome. Superantigens are also the suspected cause of numerous diseases displaying characteristic symptoms with unknown causes.
Rather than typical presentation by major histocompatibility complex type II molecules (MHC II) of antigen-presenting cells to T-cell receptors (TCRs) inside specialised clefts, superantigens bind externally to the Vβ domain of the TCR and to the complementary chain of MHC II, causing inappropriate, antigen-independent T-cell activation. In a typical infection, 0.01% of the body's T-cells are activated; superantigen-mediated infections commonly activate 5% and can reach levels of up to 25% T-cell activation. These T-cells are of all populations (helper T cells, cytotoxic T cells, suppressor T cells, and as-yet-unidentified T-cell populations), and leads to a mass activation of multiple, often contradictory, chemical mediators that contribute to the general unwellness of an individual.
Research into superantigen treatment focuses on the use of polyspecific immunologlobulin G, antagonistic peptides, and toxoid vaccines. There is concern that bacterial superantigens may be mass-produced and used as bioweapons (Staphylococcus aureus B enterotoxin, for example - *).
Interestingly, superantigens have been shown to prevent and heal autoimmune disorders in animal experiments if the timing of administration is "just right".
Clinical notes
Diseases associated with superantigen production
- Food poisoning (Staphylococcus and Staphylcoccus)
- Toxic shock syndrome (Staphylococcus)
- Wegener's granulomatosis (Staphylococcus)
- Scarlet fever (Streptococcus)
- Yersinia pseudotuberculosis
- Mycoplasma arthriditis
Diseases in which superantigen production is suspected
- Kawasaki disease
- Allergic sinusitis
- Cytomegalovirus (with HIV)
- Epstein-Barr Virus (with HIV)
- Type I diabetes mellitus
- vasculitis and other unexplained inflammatory diseases
External links
"Superantigen"