Natural Killer Cells

Despite their infuriated name, natural killer cells are literally a very important type of cell in the human body. Natural killer cells, also known as NK cells, are primarily a supportive type of cell which aids in protecting you from distinct infections and even cancer, as these cells target tumor cells.

1 The natural killer cell plays a severe role in administering the innate and adaptive immune response to pathogens, injury, and stress. Natural killer cells acquired their name from the fact that they are propagated naturally by the body and their sole purpose is to search for and suppress destructive cells.

When a destructive cell is detected, natural killer cells bind to the invader and produce a cytotoxic chemical.1 This chemical is called tumor is called tumor necrosis factor (TNF) and it is indeed a type of chemotherapy drug.1 Once the TNF has been emanated, holes begin to develop in the membrane of the invading cell. Because of the holes, fluids slip in, ultimately resulting in the cell bursting. Although originally portrayed as primarily a lytic cell, the NK cell has transpired as a cell adequate of the helper function, expansion, contraction, and accelerated memory responses; features similar to other adaptive immune cells.

1 These characteristics place the NK cell in a exclusive position, with a superior role in sculpting the host response to damage and injury.

Natural killer cells comprise 5% to 20% of human peripheral blood lymphocytes and are acquired from CD34+ hematopoietic progenitor cells.2 The precise physiologic sites where NK cells mature and the mechanisms that drive the development of their functional characteristics have not yet been utterly clarified but recent studies show that these occur in the bone marrow and the lymph nodes.

2 Born to kill, these cells were thought to voyage straight from the bone marrow, where they are manufactured, to the blood, circulating there and infiltrating the sites of early tumors or infectious agents in the body. Natural killer cells, as components of the innate immune system, are the first line of defense against cancerous cells and infectious agents.3 In other words; they do not desire prior exposure tothe antigen to elicit a response. In fact, NK function was originally construed by the cell’s ability to kill NK-sensitive tumor cells.

4.Natural killer cells can kill a ample range of cancer cells and are a promising tool for cell therapy of cancer. In the setting of the hematopoietic stem-cell transplantation, donor NK cells may employ an anti-leukemia effect if they do not express the killer-cell immunoglobulin-like receptors (KIRs) reaching with the human leucocyte antigen (HLA) class 1 epitope expresses by the patient’s leukemia cells.

2 According to the journal article, “The Korean Journal of Laboratory Medicine,” in animal models, donor NK cells killed host leukemic cells and lymphohematopoietic cells without affecting non-hematopoietic tissues, suggesting the possibility of an NK-mediated graft-versus-leukemia (GVL) effect without systemic disease.2 Therefore, it is now a typical practice at some clinical centers to select donors with an HLA and KIR type that facilitates NK cell activation. However, although the results of NK-based immunotherapeutic treatment of cancer are promising in the experimental models, their clinical effectiveness in human trials has been modest.

This is seemingly due to tumor avoidance by alteration of NK cell function and resistance to killing affiliated with tumor progression and chronic inflammation.5 For the future, a good control upon NK cell activity based on a deep knowledge of their primary physiology at the bench is perhaps one of the more promising tools for the management of human cancer in clinical applications.

The treatment of individuals with human autoimmune diseases and the triumph of improvements in their aspect of life still remains a challenge, despite the increasing knowledge of the immunological basis of these diseases. Because of NK cells potential auto reactivity or through their interaction with dendritic cells, macrophages or T lymphocytes, thereby inducing excessive inflammation or favoring the adaptive autoimmune response, Natural killer cells may be precisely involved in autoimmune diseases.

6 Studies on NK cells and NK cell receptors are therefore of high interest. According to the article, “Natural Killer Cells in Human Autoimmune Diseases,” in autoimmune disease only a few studies, mainly descriptive have been suggested.

In human autoimmune disease only a few studies, mainly descriptive, have demonstrated qualitative and quantitative modification of NK cells.6 These changes were observed on blood or tissue-infiltrating NK cells. Taken together with the expanding knowledge of the genetically variability of NK cell receptors and NK cell physiology, these findings pave the way for the dissection of the role of the NK cells in human autoimmune diseases.

Thus, NK cells may be implicated in the onset, the maintenance or the progression of autoimmune diseases.6 Some reports further suggest the involvement of NK cells in the treatment of human autoimmune disease by biotherapies.7 All of those observations propose that NK cells are involved in the complex processes of autoimmune diseases. This knowledge might allow the development of new therapeutic strategies based on NK cells for the treatment of some autoimmune diseases.

General research has been conducted on Natural Killer cells. Scientists at Barrow Neurological Institute have recently made discoveries about a type of cell that may limit inflammation in the Central Nervous System (CNS); a finding that could have important implications in the treatment of brain disorders such as multiple sclerosis.8 The research, led by Barrow’s Fu-Dong Shi, MD, PhD, is unveiling vital discoveries about how NK cells work in the CNS.

In multiple sclerosis, the body’s immune system attacks myelin, a protective sheath surrounding nerve cells in the brain and spinal cord.8 By studying a pre-clinical model of multiple sclerosis, the Barrow research revealed that enriching an affected area with NK cells reformed disease symptoms, while blocking NK cells to the CNS made symptoms worse. The research indicates that NK cells, especially those that originate in the CNS, as opposed to NK cells from peripheral organs, play a critical role in controlling the magnitude of CNS inflammation and immune response.

8 “These studies replenish novel insight into the biology of NK cells and might lead to the design of NK cell-based approaches for intervention in inflammatory and autoimmune disorders of the central nervous system,” says Dr. Shi.8 These findings have important implications for perceiving the effectiveness of some drugs currently used in the CNS diseases such as several sclerosis.

Although people often talk about how Natural Killer cells aid to fight off numerous infectious as well as cancer, these cells can also have an adverse aftermath. In some women, NK cells can over react to a potential pregnancy, ambushing the embryo. This terminal result is a miscarriage. This transpires because the natural immune system response of the NK cells goes into overdrive; meaning the NK cells vision the embryo as a cancer cell and decides to take action.

9 Once the embryo has been identified as an “invader”, your NK cells will multiply in quantity in order to have furthermore killing power.9 They will then bind to the embryo and kill it in the same way they would any other cell. Because this is not a essential response of the immune system, it is prone that you will experience multiple miscarriages due to NK cells.10 Nonetheless, with a proper diagnosis and treatment; it is viable to successfully achieve pregnancy.

Natural killer cells are a strain of cytotoxic lymphocyte that constitutes a superior component of the innate immune system. NK cells play a dominant role in the rejection of tumors and cells infected by viruses. They kill cells by releasing small cytoplasmic granules of proteins called perforin and granzyme that cause the target cell to die by apoptosis.1 Natural killer cells are a very vital type of cell in the human body that is responsible for many functions and is still being researched on today by many scientists.

The improved perceptive of NK cell deficiency in disease has opened a way for therapies precisely designed to improve NK cell function.2 The significance of NK cells in health and the repercussion of NK cell deficiency or excess are likely to be beyond extensively advised in the future. Work Cited

1. Michael T. Lotze, Angus W. Thompson. Natural Killer Cells: Basic Science and Clinical Application. London: Academic, 2010. 678 p.

2. Duck Cho, M.D., Dario Campana, M.D. The Korean Journal of Laboratory Medicine: Expansion and Activation of Natural Killer Cells for Cancer Immunotherapy. Korean J Lab Med.2009 April; 29(2): 89-96.

3. Campbell, Kery S., Colonna, M. Natural Killer Cell Protocols: Cellular and Molecular Methods. [Internet]. In methods in molecular biology; 121. Humana Press; 2000 [cited 2011 November 19]. Available from: http://libcat.jcsu.edu/search/X?SEARCH=natural+killer+cells Also available in paper copy from the publisher

4. Science Daily [Internet]. [cited 2011 November 19]. Available from: http://www.sciencedaily.com/releases/2004/02/040206075307.htm

5. Zamai Loris, Ponti Cristina. 2007. Natural Killer Cells and Cancer: The Journal of Immunology. The American Association of Immunologists, Inc., 178: 4011-4016.

6. Schleinitz, N., Vely, F., Harl, J.-R., Vivier, E. 2010. Natural Killer Cells in Human Autoimmune Diseases. Immunology, 131: 451-458.

7. JAneway, Charles A. 2001. Immunobiology: The Immune System in Health and Disease. 5th ed. New York: Garland Science. 928 p.

8. D.I. Campagnolo, R. Xiang, A. La Cava, L. Van Kaer, F.-D. Shi. Central Nervous System (CNS) – resident natural killer cells suppress Th17 responses and CNS autoimmune pathology. Journal of Experimental Medicine, 2010; 207 (9).

9. SharedJourney [Internet]. Natural Killer Cells [cited 2011 November 19]. Available from: http://www.sharedjourney.com

10. [RCOG] Royal College of Obstetricians and Gynecologists. 2004. Fertility: Assessment and Treatment for People with Fertility Problems. London: RCOG Press. 363 p.