(a) Exogenous b) Endogenous superantigen superantigen TH cell TH cell TCR TCR B Peptide for which TCR Superantigen Superantigen is not Class IⅡMHC specific B Class II MHC APC APC 超抗原参与的T细胞活化的作用示意图超抗原参与的T细胞活化的作用示意图