Cytotoxic T cells (TC or CTL, abbreviated as cytotoxic T cells) are also called killer T cells, TC cells, cell-killing T cells, or CD8+ T cells. They are a type of T cell that can kill cancer cells, virus-infected cells, and other damaged cells. Cytotoxic T cells are members of the acquired immune system. When their killing activity begins to manifest, the activity of NK cells belonging to the innate immune system will gradually decrease.

Most cytotoxic T cells express T cell receptors (TCRs), which can recognize specific antigens, which are often produced by cancer cells and viruses. Intracellular antigens bind to the first type of MHC molecules and are brought to the cell surface for T cell recognition. Once a T cell recognizes a specific antigen through the T cell receptor, it will destroy the cell.

Some T cell receptors contain a glycoprotein called CD8 that can bind to MHC1 molecules, so these cells are also called CD8+ T cells.

CD8 T cells that bind to the first MHC molecule will develop into cytotoxic T cells, and the CD8 molecule will continue to firmly grasp the first MHC molecule and prevent the target cell from leaving to carry out cytotoxic killing.

For more information, please refer to –> Strong cytotoxic T cell response to internal viral components is associated with mild COVID-19 disease