This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Superantigens are - 
Select and explain. 
A. Erythrotoxin of staph. Aureus, B. CI. Difficile toxin, C. Staphyloccocal toxic shock syndrome toxin, D. Cholera toxin
A: Erythrotoxin of staph. Aureus
Answer: A: Erythrotoxin of staph. Aureus 
Explanation: 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 . Eg: S. Aureus (enterotoxins), Group A streptococci (pyrogenic exotoxin), HIV(Nef), Rabies virus (nucleocapsid protein) etc.... Ref: Ananthanarayan & Panikers textbook of microbiology 9th edition pg:90