十万个为什么·科学启蒙30篇（4）
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How Vaccines Train the Immune System
为什么疫苗能帮助预防疾病
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Vaccines introduce harmless versions of pathogens—such as weakened viruses, protein fragments, or mRNA blueprints.
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These trigger dendritic cells to present antigens to T and B lymphocytes, launching a targeted immune response.
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Memory B cells remain ready to produce antibodies within hours if the real pathogen invades later.
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Memory T cells recognize and destroy infected cells faster, stopping disease before symptoms appear.
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Multiple doses boost immunity by encouraging stronger, longer-lasting memory cell production.
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Herd immunity emerges when enough people are vaccinated, reducing transmission and protecting those who cannot be.
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Side effects like sore arms or mild fever show the immune system is actively learning—not that the vaccine caused illness.
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mRNA vaccines don’t alter DNA; they simply instruct cells to make one safe viral protein for recognition.