Final answer:
Bacterial super antigens bind to the MHC II molecules of APCs and the variable region of the TCR β chain, causing an unregulated release of cytokines and excessive inflammation.
Step-by-step explanation:
Bacterial super antigens act by binding to both the MHC II molecules of APCs and the variable region of the TCR β chain outside the normal antigen-binding cleft (Figure 18.19). This leads to an uncontrolled release of cytokines, resulting in excessive inflammation and potentially life-threatening symptoms. Superantigens can be produced by certain bacterial and viral pathogens, triggering an unregulated immune response.