Multiple choice

Superantigens are toxins produced by many pathogenic bacteria and viruses. Which of the following statements regarding superantigens is FALSE?

  1. Staphylococcal toxic shock syndrome is an example of superantigen associated disease.

  2. Superantigen associated diseases are characterized by markedly elevated circulating levels of pro-inflammatory cytokines.

  3. In humans, a superantigen reacts with approximately 1 in 50 T-cells.

  4. Superantigens activate large numbers of B-cells.

  5. The first bacterial SAg was isolated by Bergdoll.
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D Correct answer
Explanation

Superantigens simultaneously activate large numbers of T-cells carrying a particular T-cell receptor Vβ gene, by binding at a site distinct from the antigen-binding groove. Since there are 50 different Vβ genes in humans, a superantigen will react with approximately 1 : 50 T-cells in contrast to a conventional peptide antigen that will react with 1 : 104 to 1 : 108 T-cells. They do not react with the BCR.

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