Which type of immunity involves the use of T cells to combat infections?

Cell-mediated immunity is specifically characterized by the involvement of T cells, which play a crucial role in the immune response. Unlike humoral immunity, which primarily relies on antibodies produced by B cells to target pathogens in body fluids, cell-mediated immunity is focused on the direct action of T cells. These cells can recognize and destroy infected cells, thereby directly combating intracellular pathogens such as viruses and certain bacteria.

T cells differentiate into various subtypes, including cytotoxic T cells that directly kill infected cells and helper T cells that assist other immune cells in their responses. This type of immunity is essential for defending against intracellular infections and for the proper functioning of the adaptive immune system, highlighting its vital role in maintaining health.

In contrast, options featuring humoral immunity, passive immunity, and innate immunity pertain to different aspects of immune responses—each utilizing different components of the immune system unrelated to the direct action of T cells. Thus, cell-mediated immunity stands out as the correct answer due to its specific reliance on T cells for combating infections.