Cell-mediated immunity, also known as cellular immunity, is a crucial defense mechanism of the immune system that is primarily mediated by specialized white blood cells called T lymphocytes or T cells. It is a complex cascade of immune responses that aim to eliminate infected cells, foreign substances, or abnormal cells, protecting the body against various pathogens such as viruses, some bacteria, and certain parasites.
During cell-mediated immunity, T cells recognize antigens (foreign molecules) displayed on the surface of infected or abnormal cells through their specific receptor molecules known as T-cell receptors. This interaction triggers T cells to become activated and differentiate into different subtypes, including helper T cells, cytotoxic T cells, and regulatory T cells.
Helper T cells secrete specific molecules called cytokines, which help coordinate and enhance the immune response by recruiting other immune cells to the site of infection or activating B cells to produce antibodies. Cytotoxic T cells, on the other hand, directly recognize and destroy infected or abnormal cells by releasing toxic substances, inducing apoptosis (programmed cell death) in the target cells.
Cell-mediated immunity plays a critical role in eradicating intracellular pathogens, controlling viral infections, eliminating tumor cells, and preventing the growth of cancer cells. It is also involved in the rejection of transplanted organs or tissues, as T cells can recognize foreign antigens presented by the donor tissue.
Overall, cell-mediated immunity is a fundamental component of the immune system that contributes to the overall protection of the body against a wide range of diseases and threats.
