Virus-infected cells attacked and killed by effector cytotoxic T cells are often surrounded by healthy tissue, which is spared from destruction

Question

A. Explain the mechanism that ensures that cytotoxic T cells kill only the virus-infected cells (the target cells).
B. What cytotoxins do cytotoxic T cells produce?

Answer 1

A. Cytotoxic T cells focus their killing machinery on target cells through a process called polarization. The cytoskeleton and the cytoplasmic vesicles containing lytic granules are oriented toward the area on the target cell where peptide:MHC class I complexes are engaging T-cell receptors. In the T cell, the microtubule-organizing center, Golgi apparatus, and lytic granules, which contain cytotoxins, align toward the target cells. The lytic granules then fuse with the cell membrane, releasing their contents into the small gap between the T cell and the target cell, resulting in the deposition of cytotoxins on the surface of the target cell. The cytotoxic T cell is not killed in this process and will continue to make cytotoxins for release onto other target cells, thereby killing numerous target cells in a localized area in succession.
B. The cytotoxins include perforin, granzymes, and granulysin, molecules that induce apoptosis (programmed cell death) of the target cell.