Core Framework & Diagram How Do NK Cells Kill Abnormal Cells?

The core difference is activation mechanism. CTL recognize specific MHC-I/peptide (antigen-specific) through TCR, requiring prior activation by a specific antigen before killing — slow (7–14 days to build memory) but extremely precise. NK cells integrate activating and inhibitory receptor signals to judge 'normal vs. abnormal' (non-specific), requiring no prior activation — fast (within hours) but with broader coverage. NK cells are more important in early infection and against MHC-I-downregulated cells; T cells are more important for late-phase precise clearance and long-term memory formation.

Primary NK cell deficiency (CNKD) is a rare primary immunodeficiency disease — patients show extremely high susceptibility to the herpesvirus family (CMV, EBV, VZV), manifesting as recurrent, severe, poorly controlled herpesvirus infections. This demonstrates NK cells' indispensability in anti-herpesvirus immunity — these viruses are particularly adept at downregulating MHC-I to evade T cells, and NK cells' Missing Self recognition is exactly the key countermeasure against this strategy.

Yes, quite significantly. Even acute alcohol consumption can cause noticeable NK cell activity and count decreases within hours. Long-term heavy drinking more significantly impairs NK cell function, associated with reduced capacity to control chronic viral infections (particularly hepatitis viruses) and elevated cancer risk. Moderate drinking (one to two drinks daily or less) has relatively smaller effects, but still produces measurable negative effects on NK cell function — particularly in the six to twelve hours after drinking.

CAR-NK equips NK cells with chimeric antigen receptors (CAR), retaining natural killing capacity (Missing Self + NKG2D recognition) while also targeting specific tumor antigens. Compared to CAR-T: NK cells can use universal donor sources (unlike T cells with GvHD risk), allowing pre-made off-the-shelf products. NK cells already have natural killing capacity against MHC-I-deficient cells, making them less vulnerable to tumor MHC-I downregulation evasion. Currently in early clinical trials — a very promising next-generation direction.