Natural Killer Cells; Play an Important Role in Innate Immune Responses to Infection
Natural killer cells, also known as NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system that controls several types of tumors and microbial infections by limiting their spread and subsequent tissue damage. Natural killer cells develop in bone marrow as well as in some extra medullar sites, such as lymph nodes, thymus, liver, and uterus. The NK cell development is controlled by both intracellular and extracellular factors. Natural killer cells were initially thought to develop exclusively in the bone marrow (BM). But, recent evidence in humans and mice suggests that they can also develop and mature in secondary lymphoid tissues (SLTs) including tonsils, spleen, and lymph nodes (LNs). Natural killer cells are an important part of the human immune system. In addition to their role in preventing infections, NK cells also have a key role in regulating the growth and remodeling of the placenta. In humans, the majority of NK cells are derived from the lining o