Which immune response involves the direct killing of infected host cells?

Cell-mediated immunity is primarily responsible for the direct killing of infected host cells. This form of the immune response primarily involves T lymphocytes, especially cytotoxic T cells, which are capable of recognizing and destroying cells that are infected with viruses or other intracellular pathogens. Upon recognizing infected cells, cytotoxic T cells bind to these cells and release perforin and granzymes, leading to the death of the infected cell.

This targeted approach is crucial in controlling infections that reside within host cells, as these pathogens can evade the antibodies produced in humoral immunity. While humoral immunity focuses on the production of antibodies against pathogens circulating in the bloodstream, it does not directly kill cells. Passive immunity involves the transfer of antibodies from one individual to another and provides immediate but temporary protection without the activation of the recipient’s immune response. Innate immunity is the first line of defense against pathogens, employing various mechanisms such as phagocytosis and inflammation, but it does not specifically target infected host cells like the adaptive cell-mediated response does.