Viral control

NK cells expand, undergo specific differentiation and acquire different sets of receptors and signaling molecules when they encounter certain types of viruses such as HIV (NKG2C, NK p10, NK p46), HCV (NKG2D, perforin, granzyme B, 2B4), CMV (NKG2C, CD57, KIRs), and EBV (NKG2A, NKG2D, CD16, 2B4). NK cells also produce high amounts of IFN-gamma and have memory-like properties if they re-encounter a known viral pathogen.⁴

Tumor control

In conjunction with cytotoxic T lymphocytes, NK cells are at the forefront of anti-tumor immune responses.⁵ NK cells secrete cytolytic granules containing the pore-forming protein perforin to opsonize target cells via induction of nonselective transport across the plasma membranes.⁶ NK secreted granules also contain granzymes A/B, which trigger apoptotic cascades in target cells. NK cells can also induce tumor cell death through death receptor pathways and cytokine secretion.⁷ As tumor cells acquire escape mechanisms to blunt and re-orient immune responses, NK cells may lose their efficacy against them. In immuno-oncology research, the potential of NK cells is being exploited as they can be expanded and manipulated (CAR-NK cells) for cell therapy transplant.^{8, 9}