Which function is mediated by T lymphocytes possessing the CT8 surface marker?

T lymphocytes that express the CD8 surface marker are primarily recognized as cytotoxic T cells. Their primary role is to eliminate cells that are infected by pathogens, such as viruses, as well as cancerous cells. CD8+ T cells achieve this by recognizing antigens presented on major histocompatibility complex (MHC) class I molecules, which are found on nearly all nucleated cells in the body. Upon recognition, these cytotoxic T cells induce apoptosis (programmed cell death) in the target cells, effectively clearing the infection or controlling tumor growth.

The function of helper T cells is associated with CD4 markers, linking them to supporting other immune responses rather than direct cytotoxic activity. Memory T cells can arise from either CD4+ or CD8+ cells and are essential for long-term immunity, but they do not directly mediate cytotoxic functions. Regulatory T cells, typically marked by the expression of CD4 and CD25, play a role in maintaining immune tolerance and preventing autoimmune reactions; they do not participate directly in killing infected or cancerous cells.

This specificity of function clearly delineates the role of CD8+ T lymphocytes as cytotoxic T cells, making the choice related to their function as the correct one.