Blood consists of red blood cells, white blood cells, platelets and plasma.
White blood cells are our warriors; the army inside our body that protects us from infectious disease and foreign invaders. They make up less than 1% of our blood.
Our body has a first line of defence, which we saw in the video on ‘bodies defence against pathogens’, but when this fails our white blood cells kick into action.
White blood cells are the cells of our immune system. There are two types of white blood cell; phagocytes and lymphocytes.
Phagocytes have a multi-lobed nucleus within cytoplasm. They are made in your bone marrow, and they actively seek out and engulf bacteria. They will even squeeze out of the blood, through capillary walls, to reach infected tissue. There are different types of phagocytes, with neutrophils being the most common.
Lymphocytes are formed in lymph nodes, which are found all around the body such as in your armpits and neck. Invading pathogens contain a chemical on their surface called antigens. The lymphocytes detect this and produce antibodies in response to it. The antibodies stick to the surface of the pathogen and kill it by either making it easier for phagocytes to ingest them, or making the pathogen burst, or by making the pathogens clump together which turns them into a sticky mess and again makes it easier for phagocytes to find them.
Each antibody is very specific; it will only attack one type of bacteria. Other lymphocytes produce antitoxins which combine with the invader’s toxins and make them harmless.
Sometimes the body cannot produce antibodies naturally or fast enough, and so we can have vaccinations to help us out. We will look at vaccinations in another video.
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