\"Superantigens\" have the ability to nonspecifically bind to a large number of
ID: 3514912 • Letter: #
Question
"Superantigens" have the ability to nonspecifically bind to a large number of V regions on TCRs and to MHC-II molecules on APCs 2. APC MHC class II Superantigen TCR T cell signal Signal Trsned uct0 A typical superantigen may crosslink MHC-II molecules to TCRs on as many as 20% of CD4+ T cells. Superantigens are distinct from "normal" antigens and they do not bind to the antigen-binding groove (see image above). In Toxic Shock Syndrome, caused by the TSST1 toxin from Staphylococcus aureus, TSST1 toxin has been demonstrated to be a superantigen that causes high fever, shock, and a diffuse erythematous rash. It can be life threatening. Given the above information, what do you think is the pathogenic basis of this syndrome?Explanation / Answer
Superantigens are potent T- cell mitogens. They, as stated in the question, bind to major histocompatibility complex class II molecules and T-cell receptor molecules bearing a particular V-B (beta) region. This leads to activation of large amount of T-cells and subsequent increase in the amount of proinflammatory cytokines. These include Interleukin-1 (IL 1) and Tumor Necrosis Factor (TNF). Although the T- cells proliferate in large amounts, TSST-1 is abound, which reduces the ability of T-cells to bind to the receptors. Increase in T-cells in the system, unbound, leads to symptoms of infection and tissue destruction. Host susceptibility also comes into play for increasing the chances of infection when there is no production of anti- superantigens antibodies.
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