A super-antigen is a bacterial product that
Superantigens Activate large populations of T cells that express paicular subsets of the T cell receptor b protein, causing massive cytokine release and subsequent host reactions. Conventional antigens bind to MHC class I or II molecules in the groove of the ab heterodimer and bind to T cells the V regions of the TCR-a and -b chains. In contrast, superantigens bind directly to the lateral poion of the TCR-b chain and MHC class II b chain T cell superantigens include staphylococcal enterotoxins and other bacterial products.
Binds to B7 and CD28 co-stimulatory molecules
Binds to the beta chain of TCR and MHC class II molecules of APC stimulating T cell activation
Binds to the CD4 + molecule causing T cell activation
Is presented by macrophages to a larger-than-normal number of T helper CD4 + lymphocytes
Basic Concepts