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If you lack Vitamin D your immune system will not be able to protect you from bacterial and viral infection    

Mar 05, 2010

     The immune system protects us from billions of bacteria, viruses, and other parasites with ease. We do not have to reflect upon the fact that while we converse with our friends, watch TV, or go to work, inside our bodies, our immune system is constantly on the alert, attacking at the first sign of an invasion by harmful organisms.
     The immune system is very complex. It's made up of several types of cells and proteins that have different jobs to do in fighting foreign invaders. One of these cells is called a killer T Cell. The killer T cell is specialized in attacking cells of the body infected by viruses and bacteria. It can also attack cancer cells. The killer T cell has receptors that are used to search each cell that it meets. If a cell is infected, it is swiftly killed. Infected cells are recognized because tiny traces of the intruder, a protein known as an antigen (similar to a finger print), can be found on their surface. The killer T cells terminate cancer cells and cells infected by a virus or bacterium.
     Vitamin D is vital in activating human immune system function to fight bacterial and viral infections. The lower levels suffered by around half the world's population may mean their immune systems' killer T cells are poor at fighting infection, scientists said on Sunday. The findings by Danish researchers could help the fight against infectious diseases and global epidemics, they said.
     The researchers found that the immune systems' killer cells, known as T cells, rely on vitamin D to become active and remain dormant and unaware of the possibility of threat from an infection or pathogen if vitamin D is lacking in the blood. "When a T cell is exposed to a foreign pathogen, it extends a signaling device or 'antenna' known as a vitamin D receptor, with which it searches for vitamin D," said Carsten Geisler of Copenhagen University's department of international health, immunology and microbiology, who led the study.
     "This means the T cell must have vitamin D or activation of the cell will cease. If the T cells cannot find enough vitamin D in the blood, they won't even begin to mobilize."
Scientists have known for a long time that vitamin D is important for calcium absorption, and that there is a link between levels of the vitamin and diseases such as cancer and multiple sclerosis. "What we didn't realize is how crucial vitamin D is for actually activating the immune system - which we know now," Dr. Geisler wrote in the study in the journal Nature Immunology.