This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts, Subject name: Pathology
[{'content': 'A super-antigen is a bacterial product that \nSelect and explain. \nA. Binds to B7 and CD28 co-stimulatory molecules, B. Binds to the beta chain of TCR and MHC class II molecules of APC stimulating T cell activation, C. Binds to the CD4 + molecule causing T cell activation, D. Is presented by macrophages to a larger-than-normal number of T helper CD4 + lymphocytes', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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.', 'role': 'assistant'}]