Biochemistry Questions / Explain the process of cytotoxic T cell activation and their role in inducing apoptosis in infected target cells. How do viruses evade cytotoxic T cell responses, and what implications does this have for the immune system?

After a cytotoxic T cell has been activated, it is able to secrete perforin to activate the caspase cascade in the target cell. The caspase cascade induces apoptosis in the target, resulting in a ‘clean death’ with no toxins or pathogen released.

Some viruses can downregulate the expression of MHC I, preventing viral proteins from being presented on the surface of the cell. However, low or non-existent MHC I on the cell-surface can increase targeting by NK cells.