免疫系统

了解人体拥有免疫系统，能够保护身体免受疾病侵害：皮肤是一道屏障，白细胞能识别并消灭细菌和病毒等病菌，疫苗则训练免疫系统在特定疾病引发疾病之前识别它们。

Know that the body has an immune system that protects against illness: the skin acts as a barrier, white blood cells identify and destroy germs (bacteria and viruses), and vaccines train the immune system to recognise specific diseases before they cause illness

学习证据 / Evidence

• 描述皮肤是身体抵抗病菌的第一道防线。
• 解释白细胞能发现并消灭体内的细菌和病毒。
• 描述疫苗的作用原理：疫苗含有减弱或灭活的病菌，能训练免疫系统识别真正的疾病。

• Describe the skin as the body's first line of defence against germs
• Explain that white blood cells detect and fight bacteria and viruses inside the body
• Describe how vaccines work: they contain weakened or inactive germs that train the immune system to recognise the real disease

评估问题 / Assessment

{{name}}能解释身体是怎样抵抗病菌的，以及为什么接种疫苗能帮助我们预防生病吗？

Can {{name}} explain how their body fights off germs — and why getting a vaccine helps protect them from getting sick?