NK cells are the rapid response force of the immune system, capable of taking action without waiting for orders.
The Core Framework: The Three-Function Model of NK Cells
| Core Dimension | Explanation |
|---|---|
| Missing Self Recognition | Checks if the cell possesses MHC-I molecules; absence or reduced expression = abnormal cell, leading to immediate killing. |
| Induced Self Recognition | Checks if the cell carries stress signals (NKG2D ligands); presence = damaged/cancerous, leading to immediate attack. |
| Antibody-Dependent Cellular Cytotoxicity (ADCC) | Identifies target cells marked by antibodies, binds via Fc receptors, and releases cytotoxic substances to kill them. |
Diagram: Core Mechanism
NK Cell Killing Decisions
↓
↓
Target Cell
↓ ExaminationNormal MHC-I + No stress signals →No attack (One of our own)
Reduced/Missing MHC-I → Attack (Signal of viral infection or cancer)
Presence of NKG2D ligands → Attack (Signal of cellular stress or DNA damage)
Marked by antibodies → ADCC attack
