Cell-Mediated Lysis

Synonyms

CTL activity, NK cell killing, antibody-dependent cell-mediated cytotoxicity, ADCC, target cell killing.

Definition

Cell-mediated lysis describes the killing of specific cellular targets by cells of the immune system. The effector cells are most often differentiated CD8+ T cells (that is, cytotoxic T lymphocytes or CTL) or natural killer cells (NK cells). In some instances CD4+ T cells can acquire a cytolytic phenotype, but this is considered rare. With regard to host defense, cell-mediated lysis plays an important role in resistance to intracellular pathogens. Specifically, CTL primarily kill host cells that are infected with viruses, whereas NK cells kill virally-infected and bacterially-infected host cells. Additionally, both CTL and NK cells recognize and kill certain types of tumor cells, and on rare instances cells infected with bacteria are targets of CTL-mediated killing.

Characteristics

An obligatory feature of cell-mediated lysis is that it involves cell-cell contact...