Final answer:
Natural killer (NK) cells are mononuclear cells that can destroy targets sensitized with antibodies through a process called antibody-dependent cell-mediated cytotoxicity (ADCC).
Step-by-step explanation:
The cells that are mononuclear and can kill target cells sensitized with antibodies are known as natural killer (NK) cells. These cells play a crucial role in the immune system by recognizing and eliminating cells that have been infected by viruses or have become cancerous. NK cells are equipped with receptors that detect the presence of antibodies adhering to a target cell, a mechanism known as antibody-dependent cell-mediated cytotoxicity (ADCC). When NK cells bind through their Fc receptors to the Fc region of antibodies that are already attached to the target cell, they are activated to release cytotoxic molecules like perforin and granzymes to induce apoptosis in the target cell.