K cells are a crucial part of the body’s innate immune system, accounting for 10-15% of white blood cells. They kill abnormal cells and can release enzymes to call other immune cells to fight disease, especially important in fighting viral infections.
The K cell, also known as the killer cell or natural killer cell, is considered a key part of the body’s innate immune system. These cells help protect the body from disease by finding and killing abnormal cells that occur in tumors, infected cells, and invasive, parasitic, or foreign cells. The K cell not only kills infected or abnormal cells within the body, it can also release enzymes that call on other types of immune cells, such as T and B cells, to a specific area of the body to fight off disease or infection . The K cell is considered to be especially important in helping the body fight off viral infection.
K cells are part of innate immunity, which means they exist as an integral part of a healthy immune system. The K cell typically accounts for 10 to 15 percent of a healthy person’s white blood cells or lymphocytes. These cells are often the first to recognize pathogenic invaders within the body and, as such, can be crucial in initiating the immune response.
The K cell is considered cytotoxic. When it encounters a cancer cell, a bacterium, another foreign cell, or a cell infected with a virus, it kills that cell by releasing a protein called perforin. Perforin pierces the outer membrane of the offending cell. The killer cell can then release granzyme, a protease that penetrates the punctured cell membrane and causes apoptosis, or cell death. Not only is the infected or invaded cell usually killed, but any viruses that replicate within it are usually killed as well.
Once the abnormal, infected, or foreign cell is destroyed, the killer cell can release enzymes it calls T and B cells, other important white blood cells, into the area to help kill the tumor or fight the infection. These cells, especially the T cells, can produce their own enzymes which can make the action of the K cells even more effective.
Natural killer cells are especially important in fighting virus infection, as their means of inducing apoptotic cell death can help prevent the virus from spreading to other cells in the body. Other immune cells can kill virus-infected cells, but often do so through cell lysis, a process that releases replicated viruses within the affected cell. Once released, the replicated viruses can spread to other nearby cells and make the infection worse.
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