Final answer:
The mismatched statement is that helper T cells directly target and kill cancer cells.
Step-by-step explanation:
The mismatched statement is:
- B cells: can be activated to produce antibodies
- regulatory T cells: release inhibitory cytokines to dampen the immune response
- helper T cells: directly target and kill cancer cells
- cytotoxic T cells: carry out cellular immune responses
B cells can indeed be activated to produce antibodies. Regulatory T cells release inhibitory cytokines to dampen the immune response. Helper T cells do not directly target and kill cancer cells; their primary function is to help activate and direct functions of immune responses. Cytotoxic T cells carry out cellular immune responses by destroying infected cells. Therefore, the mismatched statement is option 3) helper T cells: directly target and kill cancer cells.