Immune System


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Our body is constantly defending against being invaded by bacteria and viruses from the environment around us, which try to get into our system. Once inside our body, the invading organisms are able to use our cells to replicate causing an infection.

Thankfully our body comes with a built in defence, known as the immune system, which is able to combat these invaders in various numbers of ways.

All the cells of the immune system are produced inside the hollow cavities of the bones within our bodies. They all start out from one special cell known as a stem cell, which then divides multiple times and is able to produce nearly any cell type. During the first division, a stem cell can either produce a myeloid or lymphoid progenitor which then determines what type of immune cell it will be. The lymphoid precursors give rise to T and B lymphocytes as well as NK cells, whereas the myeloid cells produce special cells known as granulocytes. Each of these different cells has a different function. On one hand, the B cells produce molecules called antibodies which are sticky and bind to invading bacteria so they can be easily removed, whereas the T cells are able to recognise and destroy viruses. The other types of immune cell roughly known as granulocytes have varying roles, including allergic responses and removal of parasites.

Together both the lymphocytes and granulocytes act to prevent us from developing any infections.