江苏省泰州市2024届高三下学期调研测试（一模）英语试题试题详情
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The human body possesses an efficient defense system to battle with flu viruses. The immune system protects against the attack of harmful microbes (微生物) by producing chemicals called antibodies, which are programmed to destroy a specific type of microbe. They travel in the blood and search the body for invaders (入侵者). When they find an invasive microbe, antibodies attack and destroy any cell that contains the virus. However, flu viruses can be a terrible enemy. Even if your body successfully fights against the viruses, with their ability to evolve rapidly, your body may have no protection or immunity from the new ones.
Your body produces white blood cells to protect you against infectious diseases. Your body can detect invading microbes in your bloodstream because they carry antigens in their proteins. White blood cells in your immune system, such as T cells, can sense antigens in the viruses in your cells. Once your body finds an antigen, it takes immediate action in many different ways. For example, T cells produce more antibodies, call in cells that eat microbes, and destroy cells that are infected with a virus.
One of the best things about the immune system is that it will always remember a microbe it has fought before and know just how to fight it again in the future. Your body can learn to fight so well that your immune system can completely destroy a virus before you feel sick at all.
However, even the most cautious people can become infected. Fortunately, medical scientists have developed vaccines (疫苗), which are weakened or dead flu viruses that enter a person's body before the person gets sick. These viruses cause the body to produce antibodies to attack and destroy the strong viruses that may invade during flu season.
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