Explanation: 👍🏻The correct answer is D. Natural killer (NK) cells possess a variety of genome-encoded receptors, some activating and others inhibitory. Activating receptors signal for NK effector functions, including killing of the target cell. One mechanism that NK cells use to kill target cells is through release of preformed granules (such as perforin and granzymes). This mechanism is identical to that of the CD8+ cytotoxic T-lymphocytes. Both types of cells target virus-infected and neoplastic cells.
👎🏻A is not correct. CD4+ T-lymphocytes (T-helper cells) are a subgroup of lymphocytes that "help" other components of the immune system establish and maximize their killing abilities. By themselves, helper T-cells do not have any cytotoxic or phagocytic activity, but have the unique ability to prime other immune cells to become activated following exposure to antigens.
👎🏻B is not correct. Dendritic cells are professional antigen-presenting cells that are similar to macrophages. They do not kill via the release of preformed granules that trigger apoptosis in target cells.
👎🏻C is not correct. Macrophages are important phagocytic innate immune cells. Additionally, they are professional antigen-presenting cells. Through the respiratory burst and the production of reactive oxygen/nitrogen intermediates, macrophages are capable of killing bacteria. However, they do not kill via the release of preformed granules to trigger apoptosis in target cells.
👎🏻E is not correct. Plasma cells are a mature form of B lymphocytes that do not have any cytotoxic activity. Plasma cells are derived from activated B lymphocytes that undergo class switching and maturation into memory cells (which retain the ability to produce a particular antibody) and plasma cells (which produce immunoglobulins).
👎🏻A is not correct. CD4+ T-lymphocytes (T-helper cells) are a subgroup of lymphocytes that "help" other components of the immune system establish and maximize their killing abilities. By themselves, helper T-cells do not have any cytotoxic or phagocytic activity, but have the unique ability to prime other immune cells to become activated following exposure to antigens.
👎🏻B is not correct. Dendritic cells are professional antigen-presenting cells that are similar to macrophages. They do not kill via the release of preformed granules that trigger apoptosis in target cells.
👎🏻C is not correct. Macrophages are important phagocytic innate immune cells. Additionally, they are professional antigen-presenting cells. Through the respiratory burst and the production of reactive oxygen/nitrogen intermediates, macrophages are capable of killing bacteria. However, they do not kill via the release of preformed granules to trigger apoptosis in target cells.
👎🏻E is not correct. Plasma cells are a mature form of B lymphocytes that do not have any cytotoxic activity. Plasma cells are derived from activated B lymphocytes that undergo class switching and maturation into memory cells (which retain the ability to produce a particular antibody) and plasma cells (which produce immunoglobulins).