Essay On Immune System

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IMMUNE SYSTEM

All living organisms are continuously exposed to substances that are capable of causing them harm. Most organisms protect themselves against such substances in more than one way --- with physical barriers, for example, or with chemicals that repel or kill invaders. Animals with backbones, called vertebrates, have these types of general protective mechanisms, but they also have a more advanced protective system called the immune system. The immune system is a complex network of organs containing cells that recognize foreign substances in the body and destroy them. It protects vertebrates against pathogens, or infectious agents, such as viruses, bacteria, fungi, and other parasites. The human immune system is the most complex.
Although there are many potentially harmful
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The other components are antigen-presenting cells, which trap antigens and bring them to the attention of lymphocytes so that thev can mount their attack.
How lymphocytes recognize antigens

A lymphocyte is different from all other cells in the body because it has about 100,000 identical receptors on its cellular membrane that enable it to recognize one specific antigen. The receptors are proteins containing grooves that fit into patterns forrned by the atoms of the antigen molecule --- somewhat like a key fitting into a lock --- so that the lymphocyte can bind to the antigen. There are more than 10 million different types of grooves in the lymphocytes of the human immune system.
When an antigen invades the body, normally only those lymphocytes with receptors that fit the contours of that particular antigen take part in the immune response. When they do, so-called daughter cells are generated that have receptors identical to those found on the original lymphocytes. The result is a family of lymphocytes, called a lymphocyte clone. with identical antigen-specific

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