A superantigen is a bacterial product that -
Superantigens are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release. Superantigens bind first to the MHC Class II and then coordinate to the variable alpha or beta chain of T-cell Receptors . Reff: Ananthanarayan & Panikers textbook of microbiology 9th edition pg:90
Binds to B7 and CD28 costimulatory 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 mactrophages to a larger-than-normal number of T helper CD4 + lumphocytes
Immunology