1. Recognition of Target Cells:
* Killer T cells have specialized receptors called T cell receptors (TCRs) on their surface.
* These TCRs recognize specific antigens, which are molecules displayed on the surface of infected or cancerous cells.
* Antigens are fragments of foreign proteins, such as viral proteins or cancer-associated proteins.
2. Activation and Proliferation:
* When a killer T cell encounters a target cell displaying the appropriate antigen, it becomes activated.
* This activation triggers the T cell to proliferate, creating more killer T cells specific for that particular antigen.
3. Destruction of Target Cells:
* Activated killer T cells release cytotoxic granules containing two key proteins:
* Perforin: Creates pores in the target cell's membrane, allowing granzyme to enter.
* Granzyme: Activates enzymes within the target cell, leading to programmed cell death (apoptosis).
* This process effectively eliminates the infected or cancerous cell without causing widespread damage to surrounding healthy cells.
4. Memory Cells:
* Some activated killer T cells become memory T cells, which persist in the body for long periods.
* These memory T cells can quickly respond to future infections or reappearances of the same antigen, providing long-term immunity.
In summary, killer T cells are essential for:
* Eliminating virus-infected cells: They prevent the spread of viral infections.
* Destroying cancerous cells: They help control tumor growth and development.
* Preventing autoimmune diseases: They help eliminate self-reactive immune cells that could attack healthy tissues.
Important Note: Killer T cells are highly specific in their actions. They only target cells displaying the specific antigen that activated them, ensuring that healthy cells are not destroyed.
