A type of T lymphocyte, marked by the CD8 protein on its surface, that is crucial in recognizing and eliminating body cells that are infected with viruses, bacteria, or other pathogens. Cytotoxic T cells are thus an essential part of the adaptive immune response. Exposure to antigenic fragments of a pathogen presented by dendritic cells causes naive T cells to become equipped to recognize the same antigen when present on the surface of an infected cell in combination with MHC class I protein. The T-cell receptor binds to the specific antigen-MHC complex on the target cell and releases lytic granules onto the target’s surface. These granules contain several types of effector molecule, including perforin. After it has dealt with one cell, the cytotoxic T cell can migrate to other infected cells and repeat the process, while avoiding uninfected bystander cells.