Which T cell type expresses the CD8 marker and specifically kills tumor or virally infected cells?

The T cell type that expresses the CD8 marker and is primarily responsible for killing tumor or virally infected cells is known as cytotoxic T cells, also referred to as CD8+ T cells. These cells play a crucial role in the immune response by recognizing and inducing apoptosis (programmed cell death) in cells that display abnormal antigenic peptides, which are often present on the surface of cancerous or infected cells.

The CD8 marker is a co-receptor that enhances the interaction between the cytotoxic T cell and antigen-presenting cells. This helps in the recognition of MHC class I molecules, which present endogenous antigens. Upon activation, cytotoxic T cells release perforins and granzymes that facilitate the death of targeted cells. Their ability to specifically identify and destroy infected or malignant cells makes them pivotal in preserving overall health and fighting diseases.

Other T cell types, such as helper T cells or T suppressor cells, have different functions in the immune response and do not carry the CD8 marker nor do they directly kill infected or cancerous cells. Helper T cells mainly assist in activating other immune cells, while T suppressor cells are involved in modulating immune responses rather than direct killing.