ESL Video Quiz: Natural killer cell

Quiz by: esale
Quiz #: 22363
(ESL Category: listening) Natural killer cell
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Of all the immune system soldiers, natural killer cells are the most aggressive. They are lymphocytes with no immunological memory and a part of your innate immune system. Natural killer cells make up about 5 to 15 percent of the total circulating lymphocyte population. Natural killer cells are called natural killers because they do not need to recognize a specific antigen before releasing their toxins and destroying a viral-infected cell or cancer cell. They target tumor cells and protect against a wide variety of infectious microbes. In several immunodeficiency diseases, including AIDS, natural killer cell function is abnormal, thus allowing the viruses to multiply inside of human cells.
Natural killer cells kill on contact. The killer cell binds to its target, aims its weapons, and then delivers a lethal burst of toxins that produces holes in the target cell’s membrane and creates events that destroy the cancer cell membrane and cleaves DNA into many pieces in a program cell death - that is apoptosis matter. After releasing its lethal package of chemicals, the natural killer cell can detach from the cancer cell and kill many other circulating abnormal cells. Indeed research has shown that most of the tumor cells that enter the circulation are destroyed during the first 24 hours, and only a few cells succeed in establishing themselves in distant organs from the primary tumor, which is called metastasis. Natural killer cells may also contribute to immuno regulation by secreting high levels of influential lymphokines. Therefore research to develop natural products to stimulate the natural killer cell activity, especially in immune suppressed patients undergoing chemotherapy for cancer, or in any viral disease such as aids or bird flu, where immune suppression occurs, is very important in the regulation of aspects of the immune system which affects our overall health.
Finally we come back to the beginning of our knowledge of the natural killer cell. Here lies a natural killer cell in a long of sheep red blood cells. These cells are perfect targets for the natural killer cell possessing no innate C one receptor. The wrath of natural killer cell is fully vivid on the surrounding sheep red blood cells. The cytotoxins completely destroy the sheep red blood cells, leaving clear plaques around the natural killer cell. There is no apoptosis event, just direct cytotoxicity. The natural killer cell is one of the key soldiers in the fight against viral and cancer growth.

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