Which type of immune response involves the activation of cytotoxic T cells?

The activation of cytotoxic T cells is a key feature of the cell-mediated immune response. In this response, T cells, particularly CD8+ cytotoxic T cells, are specifically activated by the presence of infected cells or tumor cells. They achieve this through recognizing antigens presented by Major Histocompatibility Complex (MHC) class I molecules on the surface of these compromised cells. Once activated, cytotoxic T cells can directly kill these infected cells by releasing perforins and granzymes, leading to apoptosis.

This immune response is crucial for controlling intracellular pathogens, such as viruses, and is distinct from the humoral immune response, which primarily involves B cells, antibodies, and the neutralization of extracellular pathogens. Passive immunity response does not involve the activation of the immune system, as it refers to the acquisition of antibodies from another individual or organism. The default immune response is not a recognized term in immunology and is not associated with a specific mechanism of immune activation. Thus, the correct identification of the cell-mediated immune response emphasizes the unique role of cytotoxic T cells in targeting and eliminating infected cells.