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Killer T Cells

Killer T cells, also known as cytotoxic T lymphocytes (CTLs), are a type of white blood cell that play a crucial role in the immune system's response to viruses, bacteria, and cancer cells. They are a subset of T cells, which are a type of lymphocyte involved in cell-mediated immunity.

Function
Killer T cells are primarily responsible for identifying and destroying infected or abnormal cells in the body. They recognize specific antigens displayed on the surface of these target cells and eliminate them through a variety of mechanisms.

Surface Receptor
The surface of killer T cells contains a specific type of receptor known as the T-cell receptor (TCR). This receptor is composed of two protein chains, α and β, which come together to form a complex structure. The TCR is responsible for recognizing antigens presented by major histocompatibility complex (MHC) molecules on the surface of target cells.

Recognition Process
The recognition process begins with the presentation of antigens by antigen-presenting cells (APCs), such as dendritic cells. APCs process and present antigens on their surface using MHC molecules. When a killer T cell encounters an APC displaying an antigen that matches its specific TCR, the TCR binds to the antigen-MHC complex, forming a stable interaction.

Activation and Killing
Once the TCR binds to the antigen-MHC complex, a series of signaling events occur within the killer T cell, leading to its activation. This includes the release of cytotoxic molecules, such as perforin and granzymes, which are responsible for inducing apoptosis (cell death) in the target cell. Additionally, killer T cells can also release cytokines that help regulate the immune response and recruit other immune cells to the site of infection.

Memory and Regulation
After successfully eliminating the target cells, some killer T cells differentiate into memory T cells. These memory cells retain the ability to recognize the same antigen and respond more quickly and effectively upon re-exposure. Killer T cells are also regulated by various mechanisms to prevent excessive immune responses and the destruction of healthy cells.

In summary, killer T cells are a vital component of the immune system, capable of recognizing and eliminating infected or abnormal cells. Their surface is equipped with T-cell receptors that allow them to detect antigens presented by MHC molecules on target cells, leading to their activation and subsequent destruction.