T cell-mediated cytotoxicity can be used for cancer immunotherapy treatments. This type of therapy includes the use of specific T-cell subsets to kill cancer cells. Most T-cells act via antigen-specific receptors, the T-Cell Receptors (TCRs), which are accompanied by a glycoprotein CD8 or CD4. Depending on which MHC class molecule the glycoprotein has to bind, CD8 or CD4 will be expressed by the T-cell.
Cancer cell killing by cytotoxic T-cells
Cytotoxic T-cells, also known as CD8+ T-cells, express their TCRs accompanied by the glycoprotein CD8. CD8+ T-cells are a type of white blood cells that are associated with effective cancer cell killing:
- During antigen-specific activation, the affinity between the CD8 glycoprotein expressed by the CD8+ T-cell, and the class I MHC molecule expressed by the cancer cell, keeps both cell types bound closely together.
- The tight binding of T-cells and cancer cells through the CD8/TCR complex and the antigen/MHC-I complex causes CD8+ T-cells to secrete perforin and granzymes, leading to cancer cell lysis.
How T-cell mediated cytotoxicity works. Illustration by: Original: Dananguyen Derivative: nagualdesign [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
T-cells that express a CD4 glycoprotein accompanied with their TCR are known as T-helper cells; they send signals to other types of immune cells, including CD8+ cytotoxic T-cells, rather than induce cancer cell lysis themselves. After recruitment, the recruited immune cell will kill the cancer cell in its turn.