Which immune response is characterized by T lymphocytes directly attacking pathogens?

Cell-mediated immunity is characterized by T lymphocytes, also known as T cells, directly attacking and destroying infected cells or pathogens. This type of immune response is crucial for eliminating intracellular pathogens, such as viruses, and is essential in recognizing and responding to cancer cells as well.

T cells operate by recognizing specific antigens presented by infected cells or professional antigen-presenting cells. Once they bind to these antigens, they become activated and can proliferate into different subsets, including cytotoxic T cells, which directly kill infected cells, and helper T cells, which assist in orchestrating the immune response.

This response is distinct from antibody-mediated immunity, where B lymphocytes produce antibodies that target pathogens in the blood or extracellular space. Innate immunity refers to the body’s first line of defense and involves physical barriers and various immune cells, while passive immunity involves the acquisition of antibodies from another source, such as maternal antibodies transferred to a fetus. Thus, the defining feature of T lymphocytes participating in the direct attack on pathogens fundamentally aligns with the concept of cell-mediated immunity.