Which type of lymphocyte is primarily responsible for cell-mediated immunity?

The correct answer is T lymphocyte, which plays a crucial role in cell-mediated immunity. T lymphocytes, or T cells, are a type of white blood cell that originate in the bone marrow but mature in the thymus gland. They are central to the adaptive immune response, particularly in recognizing and responding to infected or damaged cells.

T cells can be further classified into several subtypes, including cytotoxic T cells, which directly attack and destroy virus-infected cells, and helper T cells, which assist other immune cells in the response. This targeted approach distinguishes cell-mediated immunity from humoral immunity, which is primarily mediated by B cells and antibodies.

In contrast, memory cells, while important in remembering past infections for a quicker response upon re-exposure, do not execute the immediate effector functions of the immune system like T cells do. Similarly, macrophages are involved in phagocytosis and also play a role in presenting antigens to T cells but do not directly mediate the cellular immune response like T lymphocytes. The term "intervention" does not correspond to a recognized type of lymphocyte in immunology.