Tuesday, September 29, 2009

Natural Killer Cell

A natural killer cell is a type of lymphocyte, which is a white blood cell that play an important role in the immune system. A natural killer cell (NK cell) is a cytotoxic lymphocyte, that is to say a toxin-containing white blood cell whose main function is to detect and kill virus-infected cells and cancer cells. In order to perform their job, natural killer cells need an activating signal, such as cytokines, which are stress-molecules released by cells when they are infected by viruses. The cytokines activate natural killer cells. Natural killer cells also act in response to chemical messages which are released from Helper T-cells (a type of white blood cells).

Natural killer cells have two type of toxic proteins in their cytoplasm, such as perforin and granzymes. When perforin is released by a NK cell, it makes pores in the cell membrane of the virus-infected cell. Once these pores have been made, the granzymes enters the target cell body, inducing apoptosis, which is the process of cell distruction, leading to the destruction of the virus inside the target cell.

Natural Killer Cells