Final answer:
Superantigens trigger an excessive inflammatory response by binding to MHC II molecules and the TCR ß chain, resulting in uncontrolled release of cytokines and potentially leading to shock and organ failure.
Step-by-step explanation:
The mechanism behind superantigens triggering the shock cascade involves their simultaneous binding to MHC II molecules of APCs and the variable region of the TCR ß chain. This binding occurs outside of the antigen-binding cleft of MHC II, resulting in the activation of MHC II and TCR without specific foreign epitope recognition.
The result is an excessive, uncontrolled release of cytokines, often called a cytokine storm, which stimulates an excessive inflammatory response. This can lead to a dangerous decrease in blood pressure, shock, multi-organ failure, and potentially, death.