Cell death occurs through various mechanisms, including programmed cell death, where the cell actively participates in its own demise. One significant example is Activation-Induced Cell Death (AICD), which is crucial in immune system regulation.
Activation-Induced Cell Death (AICD)
AICD is a type of programmed cell death that occurs specifically in T-cells. This process involves:
- Repeated Stimulation: Repeated activation of specific T-cell receptors (TCR) triggers AICD. This typically occurs when T-cells are continuously exposed to antigens.
- Fas-Fas Ligand Interaction: Repeated stimulation of T-cell receptors leads to the interaction of the Fas receptor (Fas, also known as CD95) on the T-cell with its corresponding ligand, FasL (Fas ligand or CD95 ligand).
- Initiation of Cell Death: The binding of FasL to Fas initiates a cascade of intracellular events resulting in the cell's apoptosis (programmed cell death).
Here’s a table summarizing the key aspects:
| Feature | Description |
|---|---|
| Cell Type | T-cells |
| Trigger | Repeated stimulation of specific T-cell receptors (TCR) |
| Key Molecules | Fas receptor (Fas, CD95) and Fas ligand (FasL, CD95 ligand) |
| Mechanism | Interaction of Fas and FasL initiates a signaling pathway leading to apoptosis. |
| Function | Maintains peripheral immune tolerance by eliminating over-activated or self-reactive T-cells. |
Why is AICD important?
- Immune Tolerance: AICD prevents excessive or harmful immune responses. By eliminating T-cells that are repeatedly activated, it helps to avoid autoimmune diseases, where the immune system attacks the body's own cells.
- Limiting Immune Response: Once an infection has been cleared, AICD helps to reduce the number of activated T-cells, ensuring the immune response is controlled.
- Preventing Hyperactivity: This type of cell death ensures that T-cells don't become overactive, which can lead to various immunological disorders.
In essence, AICD is a highly regulated and programmed mechanism to maintain balance and prevent damage within the immune system by causing cell death in repeatedly stimulated T-cells.
