Question A: The patient has suffered toxic shock, caused by the exotoxin of Staphylococcus aureus. This exotoxin is classed as a superantigen and binds MHC II molecules differently to normal antigens. In fact, it does not need to be bound to MHC II to activate helper T cells.
Question B: The unusual binding of the superantigen causes the helper T cells to massively overproduce cytokines, which cause the toxic shock. You explain to your patient that the immune response is a potent response and will cause problems if it malfunctions, but as we live surrounded by pathogens we need such a system to keep us alive.