Natural killer (NK) cells are nonspecific.
Unlike B cells and T cells, which recognize specific antigens, natural killer cells operate differently. According to the provided reference, NK cells are not antigen specific. This means they do not target pathogens or infected cells based on identifying a unique molecular signature (antigen) associated with that specific threat.
Instead, their activation relies on a balance of signals received through various cell-surface receptors. The decision for an NK cell to attack is influenced by the differential engagement of these activating and inhibitory receptors on target cells. Furthermore, proinflammatory cytokines also play a crucial role in stimulating NK cell activity. This mechanism allows NK cells to recognize and eliminate abnormal cells, such as tumor cells or virus-infected cells, that may downregulate molecules typically recognized by inhibitory receptors, thereby triggering NK cell activation.
How NK Cells are Activated (Instead of Antigen Specificity)
Based on the reference, NK cell activation involves:
- Differential Receptor Engagement: A balance between signals from activating and inhibitory receptors on the NK cell surface.
- Proinflammatory Cytokine Stimulation: Signals from cytokines that enhance their killing function.
This non-antigen-specific mode of operation makes NK cells a vital part of the innate immune system, providing a rapid response against threats before the adaptive immune system mounts an antigen-specific defense.
