| 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 are almost all have antigenic
properties, but rather receive their name from their powers to induce the production of antibodies.
Symptoms
Characteristic sysmptoms of superantigen-mediated diseases include:
Chronic infection can cause autoimmune diseases and glomurelonephritis.
Pathophysiology
Superantigens are secreted as exotoxins by bacteria, alterantively 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
bodies 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 (T-helper cells, T-cytoxicity cells, T-suppressor cells and as yet unidentified
populations of T-cells), 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, anatgonistic peptides and toxoid vaccines.
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
Diseases in which superantigen production is suspected
External links
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