Which type of immune cell is primarily involved in cell-mediated defense?

The immune cell primarily involved in cell-mediated defense is T cells. These cells play a crucial role in the adaptive immune response, particularly in identifying and eliminating infected or dysfunctional cells. T cells can differentiate into various subtypes, with cytotoxic T cells (also known as CD8+ T cells) being specifically responsible for attacking and destroying cells harboring viruses or other intracellular pathogens.

In addition to dealing with infected cells, T cells also assist in orchestrating the immune response by interacting with other immune cells, such as B cells, to enhance antibody production. This cell-mediated immunity is vital, especially for defending against pathogens that reside within host cells, as antibodies produced by B cells cannot penetrate these cells. Thus, T cells are essential for their ability to recognize and eliminate threats at the cellular level, making them the core players in cell-mediated immune defense.