Superantigens cause an overreaction of the immune system, leading to diseases such as toxic shock syndrome and Kawasaki disease. They are produced by some bacteria and viruses and are highly resistant to heat and protein-degrading enzymes.
Superantigens are proteins that cause T cells of the immune system to overreact to infection. They are produced by some infectious bacteria and viruses. The overreaction of the immune system to the antigen causes a group of diseases that manifest with fever and shock, such as food poisoning, toxic shock syndrome, and Kawasaki disease.
Common bacterial species that can use a superantigen as part of their virulence strategy are staphylococci and streptococci. These bacteria usually live harmlessly on the body, but can cause infections under certain circumstances. Superantigens of each species are, like antigens, molecules that the immune system recognizes as foreign.
Superantigens cause disease symptoms by causing the T cells of the immune system to overreact to these molecules. Parts of a bacterium or virus are usually recognized by the macrophage cells of the immune system. The macrophage ingests the foreign invaders and breaks them down. Then the macrophage takes parts of the broken down invader or other molecule it has ingested and sends the fragments out of the cell using a major histocompatibility complex (MHC) to hold onto the fragment.
A T cell arrives and uses its T cell receptor molecule outside its own cell to bind to the fragment. Once the T cell recognizes the fragment, it initiates an immune response. Each T cell recognizes some MHC and some fragments and usually responds only to those particular stimuli. Superantigens bind to the MHC presenter molecule differently than regular antigens, so more T cells are induced to recognize the superantigen fragment than would a normal fragment.
A normal antigen causes 0.001 percent to 0.0001 percent of T cells to mount an immune response. A superantigen causes 2% to 20% of T cells to produce a response. When a T cell is exposed to a normal antigen, it releases molecules with immunological action, and these molecules lead to the normal inflammatory pathway, designed to help rid the body of infection. A superantigen activates many more T cells than normal antigens, so this inflammatory response is exaggerated and fever, rash, low blood pressure, and shock can occur.
Superantigens are medium-sized proteins that are highly resistant to heat and protein-degrading enzymes. These characteristics help proteins survive cooking and digestive enzymes, making superantigens important virulence factors in foodborne disease. They also play a role in autoimmune diseases, toxic shock syndrome, diabetes and Kawasaki disease, a leading cause of acquired heart disease in children.
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