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What is a Superantigen?

A superantigen is a potent molecule that hyperactivates our immune system, often leading to severe reactions. Unlike ordinary antigens, superantigens can trigger a massive immune response by binding to specific receptors on immune cells. This can result in conditions ranging from food poisoning to toxic shock syndrome. Intrigued by how these tiny entities wield such power? Let's examine their impact on our health.
Jillian O Keeffe
Jillian O Keeffe

Superantigens are proteins that cause the T-cells of the immune system to over-react to infection. They are produced by certain infectious bacteria and viruses. The immune system over-reaction to the antigen causes a group of diseases that manifest in fever and shock, such as food poisoning, toxic shock syndrome and Kawasaki disease.

Common bacterial species that may 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 in certain circumstances. The superantigens of each species are, like antigens, molecules the immune system recognizes as foreign.

Superantigens can cause a fever, rash, low blood pressure and other symptoms.
Superantigens can cause a fever, rash, low blood pressure and other symptoms.

Superantigens cause symptoms of illness by tricking the T-cells of the immune system into over-reacting to these molecules. Parts of a bacterium or a 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 molecules that it ingested and posts the fragments on the outside of the cell using a major histocompatibility complex (MHC) to hold the fragment.

Rheumatoid arthritis is cause by an overreaction of the immune system.
Rheumatoid arthritis is cause by an overreaction of the immune system.

A T-cell comes along and uses its T-cell receptor molecule on the outside of its own cell to bind to the fragment. Once the T-cell recognizes the fragment, it begins an immune response. Each T-cell recognizes certain MHCs and certain 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 tricked into recognizing the superantigen fragment than would recognize a regular fragment.

Superantigens cause symptoms of illness by tricking the T cells of the immune system into over-reacting to these molecules.
Superantigens cause symptoms of illness by tricking the T cells of the immune system into over-reacting to these molecules.

A normal antigen causes from 0.001 percent to 0.0001 percent of T-cells to produce an immune response. A superantigen causes from 2 percent to 20 percent 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, which is designed to help rid the body of infection. A superantigen activates many more T-cells than regular antigens, so this inflammatory response is exaggerated, and fever, rash, low blood pressure and shock can occur.

Superantigens play a role in diabetes and other diseases.
Superantigens play a role in diabetes and other diseases.

Superantigens are medium-size proteins that are highly resistant to heat and to protein-degrading enzymes. These characteristics help the proteins to survive cooking and digestive enzymes, making superantigens important virulence factors in food-borne 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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    • Superantigens can cause a fever, rash, low blood pressure and other symptoms.
      By: Photographee.eu
      Superantigens can cause a fever, rash, low blood pressure and other symptoms.
    • Rheumatoid arthritis is cause by an overreaction of the immune system.
      By: rob3000
      Rheumatoid arthritis is cause by an overreaction of the immune system.
    • Superantigens cause symptoms of illness by tricking the T cells of the immune system into over-reacting to these molecules.
      By: extender_01
      Superantigens cause symptoms of illness by tricking the T cells of the immune system into over-reacting to these molecules.
    • Superantigens play a role in diabetes and other diseases.
      By: Monkey Business
      Superantigens play a role in diabetes and other diseases.