A superantigen is a bacterial product that
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 macrophages to a larger-than-normal number of T helper CD4 + lymphocytes
stimulates massive amounts of IgG synthesis because of its large size