This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'a super antigen is a bacterial product that \nSelect and explain. \nA. Binds to B7 and CD 8 co stimulatory molecules, B. Binds to beta chain of TCR and MCH class 2 molecules at APC stimulating T cell activation, C. Binds to CD4 molecules causing TCells activation, D. Is presented by macrophages to a larger than normal number of T helper CD4 lymphocytes', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ref Harrison 16/e p1920 Superantigens (SAgs) are a class of antigens that result in excessive activation of the immune system. Specifically it causes non-specific activation of T-cellsresulting in polyclonal T cell activation and massive cytokine release. SAgs are produced by some pathogenic viruses and bacteria most likely as a defense mechanism against the immune system.Compared to a normal antigen-induced T-cellresponse where 0.0001-0.001% of the body's T-cells are activated, these SAgs are capable of activating up to 20% of the body's T-cells. Fuhermore, Anti-CD3and Anti-CD28 Antibodies (CD28-SuperMAB) have also shown to be highly potent superantigens (and can activate up to 100% of T cells).", 'role': 'assistant'}]