Answer
Cytotoxic T cells (CD8+ T cells) are specialized immune cells that play a crucial role in eliminating infected or abnormal cells from the body. They use several mechanisms to destroy target cells, primarily those that are infected with viruses, intracellular bacteria, or cancerous cells. Here are some ways in which cytotoxic T cells destroy target cells:
1. **Perforin and Granzyme Release:**
- Cytotoxic T cells release perforin, a protein that forms pores on the target cell's membrane. These pores create channels that allow other molecules to enter the target cell.
- Once perforin has created pores, cytotoxic T cells release granzymes, which are protease enzymes. Granzymes enter the target cell through the perforin pores and trigger a cascade of events that lead to apoptosis (programmed cell death).
2. **Induction of Apoptosis:**
- Granzymes released by cytotoxic T cells activate caspases, which are enzymes involved in the apoptotic pathway.
- Activation of caspases leads to the breakdown of cellular components and DNA fragmentation, ultimately causing the target cell to undergo apoptosis.
3. **Fas Ligand-Fas Receptor Interaction:**
- Cytotoxic T cells express a protein called Fas ligand (FasL) on their surface.
- When FasL on the cytotoxic T cell binds to its receptor, Fas, on the target cell's surface, it triggers a signal that also leads to apoptosis.
4. **Release of Cytokines:**
- Cytotoxic T cells release cytokines such as tumor necrosis factor (TNF) and interferon-gamma (IFN-γ) that contribute to the destruction of target cells.
- These cytokines can enhance the activity of other immune cells, increase inflammation, and promote the immune response against the target cells.
5. **Detachment from Blood Supply:**
- Cytotoxic T cells can target endothelial cells that line blood vessels supplying oxygen and nutrients to tumors.
- By destroying these endothelial cells, cytotoxic T cells can interrupt the blood supply to tumors, causing necrosis and limiting their growth.
The combination of these mechanisms ensures that cytotoxic T cells can efficiently detect and eliminate infected or abnormal cells in a highly specific manner, while minimizing damage to surrounding healthy tissue. This process is a crucial component of the immune response against intracellular pathogens and cancerous cells.
Work Step by Step
Cytotoxic T cells (CD8+ T cells) are specialized immune cells that play a crucial role in eliminating infected or abnormal cells from the body. They use several mechanisms to destroy target cells, primarily those that are infected with viruses, intracellular bacteria, or cancerous cells. Here are some ways in which cytotoxic T cells destroy target cells:
1. **Perforin and Granzyme Release:**
- Cytotoxic T cells release perforin, a protein that forms pores on the target cell's membrane. These pores create channels that allow other molecules to enter the target cell.
- Once perforin has created pores, cytotoxic T cells release granzymes, which are protease enzymes. Granzymes enter the target cell through the perforin pores and trigger a cascade of events that lead to apoptosis (programmed cell death).
2. **Induction of Apoptosis:**
- Granzymes released by cytotoxic T cells activate caspases, which are enzymes involved in the apoptotic pathway.
- Activation of caspases leads to the breakdown of cellular components and DNA fragmentation, ultimately causing the target cell to undergo apoptosis.
3. **Fas Ligand-Fas Receptor Interaction:**
- Cytotoxic T cells express a protein called Fas ligand (FasL) on their surface.
- When FasL on the cytotoxic T cell binds to its receptor, Fas, on the target cell's surface, it triggers a signal that also leads to apoptosis.
4. **Release of Cytokines:**
- Cytotoxic T cells release cytokines such as tumor necrosis factor (TNF) and interferon-gamma (IFN-γ) that contribute to the destruction of target cells.
- These cytokines can enhance the activity of other immune cells, increase inflammation, and promote the immune response against the target cells.
5. **Detachment from Blood Supply:**
- Cytotoxic T cells can target endothelial cells that line blood vessels supplying oxygen and nutrients to tumors.
- By destroying these endothelial cells, cytotoxic T cells can interrupt the blood supply to tumors, causing necrosis and limiting their growth.
The combination of these mechanisms ensures that cytotoxic T cells can efficiently detect and eliminate infected or abnormal cells in a highly specific manner, while minimizing damage to surrounding healthy tissue. This process is a crucial component of the immune response against intracellular pathogens and cancerous cells.
