Innate immune responses thought to be involved in defense against tumors include

Innate immune responses thought to be involved in defense against tumors include

• A. NK cell-mediated apoptosis.
• B. MHC I-restricted T-cell-mediated destruction.
• C. ADCC.
• D. all of the above.

Answer: (A)

Natural killer (NK) cells are key players in innate tumor surveillance. They can recognize stressed or transformed cells that often have reduced MHC I or display stress-induced ligands, and trigger target cell death without prior sensitization. This cytotoxic action is mainly through perforin and granzymes, leading to apoptosis, or via death receptor pathways. Because it doesn’t require antigen-specific activation or antigen presentation, it fits the innate response profile. In contrast, destroying tumor cells via MHC I–restricted T cells depends on antigen presentation and clonal expansion of CD8+ T cells—hallmarks of adaptive immunity. ADCC involves antibodies binding to tumor cells and recruiting effector cells through Fc receptors; while important, it relies on antibodies produced by B cells, linking to the adaptive system rather than representing a pure innate mechanism.

Natural killer (NK) cells are key players in innate tumor surveillance. They can recognize stressed or transformed cells that often have reduced MHC I or display stress-induced ligands, and trigger target cell death without prior sensitization. This cytotoxic action is mainly through perforin and granzymes, leading to apoptosis, or via death receptor pathways. Because it doesn’t require antigen-specific activation or antigen presentation, it fits the innate response profile.

In contrast, destroying tumor cells via MHC I–restricted T cells depends on antigen presentation and clonal expansion of CD8+ T cells—hallmarks of adaptive immunity. ADCC involves antibodies binding to tumor cells and recruiting effector cells through Fc receptors; while important, it relies on antibodies produced by B cells, linking to the adaptive system rather than representing a pure innate mechanism.