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A unique feature of the vertebrates was the way they could fight infections. They have cells called lymphocytes which invertebrates did not have. Each lymphocyte is able to make a protein called an antibody. Every lymphocyte makes a different antibody from all other lymphocytes.
When a lymphocyte meets an invading cell its antibody might stick to a part of the enemy. From all the millions of different lymphocytes at least one has an antibody which will stick. This lymphocyte then begins to reproduce itself in large numbers. Some lymphocytes attack the invader they have stuck to. Others release their antibody, which is carried round in the blood and sticks to invaders in other parts of the body. Different cells called phagocytes can recognize cells with antibody sticking to them, and attack and kill them. This two-pronged attack upon invaders is called the immune system. Once lymphocytes have fought off an attack they never forget. Next time the animal is infected with the same disease it can fight it off much more quickly. Cells of the immune system are made in bone marrow, which is why no animals but vertebrates have this wonderful system. |
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Useful Links |
Biological Environment > Immune System
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This site tells the story of the history of the universe. Click Earlier and Later to follow the story.
Note: Many facts have been simplified to make them easier to understand.
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Note: Many facts have been simplified to make them easier to understand.
Click here to read Time Crystal, history of the Universe as sci-fi fantasy romance!
