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为什么疫苗能帮助预防疾病

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

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

Multiple doses boost immunity by encouraging stronger, longer-lasting memory cell production. 多次接种可增强免疫力，促进更强、更持久的记忆细胞生成。
Vaccines introduce harmless versions of pathogens—such as weakened viruses, protein fragments, or mRNA blueprints. 疫苗引入无害的病原体形式，例如减毒病毒、蛋白质片段或mRNA蓝图。
Memory T cells recognize and destroy infected cells faster, stopping disease before symptoms appear. 记忆T细胞能更快识别并清除受感染细胞，在症状出现前阻断疾病发展。

这篇中文题目最接近哪一句？为什么疫苗能帮助预防疾病一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？疫苗引入无害的病原体形式，例如减毒病毒、蛋白质片段或mRNA蓝图。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） How Vaccines Train the Immune System How to cook noodles A maths worksheet

Multiple doses boost immunity by encouraging stronger, longer-lasting memory cell production.

Multiple doses boost immunity by encouraging stronger, longer-lasting memory cell production.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：Multiple doses boost immunity by encouraging stronger, longer-lasting memory cell production.