From the Research
The answer is (e) natural killer cells. Natural killer (NK) cells are a type of lymphocyte that exhibits spontaneous antitumor activity without prior sensitization or activation, as highlighted in a recent study published in 2023 1. Unlike cytotoxic T cells, which require recognition of specific antigens presented on MHC molecules and prior activation, NK cells can directly recognize and kill tumor cells without prior exposure. They identify abnormal cells through the detection of "missing self" (reduced MHC class I expression) and "induced self" (stress-induced molecules) on tumor cells. NK cells release cytotoxic granules containing perforin and granzymes that induce apoptosis in target cells. They also produce cytokines like interferon-gamma that enhance the overall immune response against tumors. This innate ability to recognize and destroy transformed cells makes NK cells a critical component of the body's first-line defense against cancer development, as further supported by studies in 2021 2 and 2022 3. Some key features of NK cells include:
- Their ability to recognize and kill tumor cells without prior sensitization or activation
- Their role in immunosurveillance and microorganism elimination
- Their potential as a cellular therapy for cancer treatment, as discussed in a study from 2021 2
- Their interdependence with cytotoxic T lymphocytes in eliminating cancer cells, as shown in a study from 2022 3. Overall, the evidence suggests that NK cells play a crucial role in spontaneous antitumor activity, making them a vital component of the immune system's defense against cancer.