Cytotoxic t cell

Cytotoxic T cell

A Cytotoxic T cell (also known as CTc, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8+ T-cell) is a type of T cell that plays a key role in the immune system, particularly in the eradication of cancer cells and cells infected by viruses. These cells are part of the adaptive immune system and have the ability to recognize and destroy infected cells, cancer cells, and cells that are damaged in other ways.

Function

Cytotoxic T cells are crucial for immune defense. They are able to recognize antigens on the surface of infected cells due to the interaction of their T cell receptor (TCR) with the antigenic peptide-MHC complex. Once the TCR binds to the antigenic peptide-MHC complex, the cytotoxic T cell triggers a lethal hit that leads to the death of the infected cell. This process is known as apoptosis.

Activation

The activation of cytotoxic T cells requires the recognition of specific antigens presented by MHC class I molecules on the surface of antigen-presenting cells (APCs). This is followed by a second signal provided by the interaction of costimulatory molecules expressed on the APC and the T cell. Once activated, cytotoxic T cells begin to proliferate and differentiate into effector cells.

Effector Function

The effector function of cytotoxic T cells is mediated by the release of cytotoxic granules that contain perforin and granzymes. Perforin forms pores in the target cell membrane, allowing granzymes to enter and initiate apoptosis. In addition to granule-mediated killing, cytotoxic T cells can also induce apoptosis through the Fas ligand/Fas pathway.

Regulation

The activity of cytotoxic T cells is tightly regulated to prevent excessive immune responses that could lead to tissue damage. This is achieved through various mechanisms, including the expression of inhibitory receptors on T cells, the production of anti-inflammatory cytokines, and the induction of regulatory T cells.

Clinical Significance

Cytotoxic T cells play a crucial role in the control of viral infections and cancer. Their dysfunction or depletion can lead to severe disease, while their activation can be harnessed for therapeutic purposes, such as in cancer immunotherapy.