How do cytotoxic T lymphocytes target virus-infected cells?

Cytotoxic T lymphocytes (CTLs), also known as CD8+ T cells, play a crucial role in the immune response against virus-infected cells. The primary mechanism by which they target these cells involves the recognition of viral antigens present on the surface of infected cells. When a cell becomes infected by a virus, viral proteins are synthesized and processed and then presented on major histocompatibility complex (MHC) class I molecules on the cell surface. CTLs have specific receptors, known as T cell receptors (TCRs), that can bind to these viral antigens displayed by MHC class I.

This recognition is critical because it allows CTLs to identify and specifically target only those cells that are presenting the viral antigens, thereby sparing healthy, uninfected cells. Once a CTL recognizes an infected cell through the binding of its TCR to the antigen-MHC complex, it can initiate a response that leads to the destruction of the infected cell. This direct targeting is essential for controlling viral infections and is a key component of the adaptive immune response.