Understanding How Cytotoxic T Lymphocytes (CTLs) Eliminate Infected or Abnormal Cells: A Comprehensive Breakdown

CTL kills the target cell

Cytotoxic T lymphocytes (CTLs) play a crucial role in the immune response by recognizing and eliminating specific infected or abnormal cells

Cytotoxic T lymphocytes (CTLs) play a crucial role in the immune response by recognizing and eliminating specific infected or abnormal cells. CTLs are a type of white blood cell called lymphocytes, which are part of the adaptive immune system.

When an infectious agent such as a virus invades the body, infected cells present fragments of the virus-derived proteins (antigens) on their surface. These antigens are recognized by specific receptors on the CTLs called T-cell receptors (TCRs).

Upon recognition of the antigen, CTLs become activated and undergo a series of complex steps to kill the target cell. Here is a detailed breakdown of how CTLs kill the target cell:

1. Recognition: The TCR of the CTL binds to the specific antigen presented on the surface of the infected or abnormal cell. This interaction is enhanced by the binding of co-receptors on the CTL with co-stimulatory molecules on the target cell.

2. Activation: Once the TCR engages the antigen, the CTL activates signaling pathways inside the cell, leading to rapid changes and the activation of various effector mechanisms.

3. Release of Cytokines: The activated CTL releases cytokines, such as interferons and interleukins, which recruit and activate other immune cells to collaborate in the immune response against the infected cell.

4. Granule Exocytosis: CTLs possess specialized secretory vesicles called lytic granules, which contain perforin and granzyme proteins. Upon activation, the CTL directs these granules towards the target cell.

5. Perforin-mediated Membrane Pore Formation: Perforin proteins are released from the lytic granules and form pores in the membrane of the target cell. These pores allow the entry of granzyme proteins into the target cell.

6. Granzyme-mediated Cell Death: Granzyme proteins, particularly granzyme B, enter the target cell through the perforin pores. Once inside the target cell, granzyme B activates caspases, which are enzymes that contribute to cell death by initiating a cascade of cellular destruction.

7. Induction of Apoptosis: Activation of caspases triggers a process called apoptosis, which is a controlled form of cell death. Apoptosis ensures the infected or abnormal cell is eliminated in a way that minimizes damage to surrounding healthy cells and prevents the release of harmful viral particles.

By following these steps, CTLs are able to specifically recognize and eliminate infected or abnormal cells, providing a crucial defense against infectious agents and contributing to the resolution of immune responses.

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