Which of the following is a superantigen ?

Ans. is 'c' i.e., TSST Superantigens Ceain species of infectious microorganisms produce powerful, immunostimulatory and disease causing toxins called superantigen, so called because of their ability to polyclonally active large fraction ( up to 20% ) of T cell population. Superantigens are potent activators of T-lymphocytes. Superantigens stimulate very large numbers of T cells, without relation to their epitope specificity. This leads to an excessive and dysregulated immune response with release of cytokines IL - 1, IL - 2, TNF - a and IF - y. Conventional antigens bind to MHC class I or II molecules in the groove of the cc 13 dimer (T cell receptor). In contrast, superantigen bind directly to the lateral poion of TCR 13 chain and MHC class II 13 chain, and stimulate T cells solely on 7 13 gene segment utilized independent of the D, J and y a - sequences present - Tf3 restricted T cell mitogens. Superantigens are capable of activating up to 20% of the peripheral T-cell pool, where as conventional antigens activate < I in 10, 000. Examples of superantigen Staphylococcal toxic shock syndrome toxin Staphylococcal enterotoxins Staphylococcal exfoliative (erythrogenic) toxin Streptococcal toxic shock syndrome toxin Ceain nonhuman retroviral proteins. Yersinia pseudotuberculosis Mycoplasma ahritis. Mouse mammary tumor virus.