Exotoxins:
Lecture 2: Type I, type II toxins and type III secretion systems.
Type I Toxins: Superantigens


Superantigens:
¸ They are microbial or viral proteins with potent immunostimulatory properties.
¸ SAgs interact simultaneously with MHC class II molecules and T cell receptors.
¸ This leads to the massive production of inflammatory cytokines like TNFa and IL-2, which can result in acute toxic shock.
¸ Superantigens are produced mostly by Staphylococcus aureus and Streptococcus pyogenes.
¸ The prototypical Sag is the Toxic Shock Syndrome Toxin-1 (TSST1) produced by some strains of S. aureus.
¸ Many genes coding for SAgs produced by S. aureus or S. pyogenes are caried by bacteriophages. SAgs will be only produced by toxigenic strains.



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