NK cell therapy

Natural killer (NK) cells are a class of innate immune lymphocytes that recognize and eliminate abnormal cells, including virally infected cells and tumor cells, without needing prior antigen exposure or the antigen-specific priming that T cells require. They distinguish target cells through a balance of activating and inhibitory receptor signals: healthy cells display surface molecules (such as MHC class I) that engage inhibitory receptors and suppress NK attack, while stressed or malignant cells often downregulate these molecules or upregulate stress ligands, tipping the balance toward activation. Upon activation, NK cells release cytotoxic granules containing perforin and granzymes, and can also produce cytokines that recruit and shape broader immune responses. NK cell therapy involves expanding and administering these cells, typically derived from a patient's own blood (autologous) or from a donor or engineered source, to increase the number of functional killer cells available to target malignant tissue. This approach is explored mainly in oncology, where tumors frequently evade T-cell-based immunity by downregulating antigen presentation machinery; because NK cells do not depend on this machinery for recognition, they offer a complementary route to attacking such tumors, either alone or alongside other immune-modulating treatments.