Immune Response
Immune response is how your body finds and fights off germs that make you sick.
Think of it this way
Your kitchen has a security system built into it. When a strange piece of food falls into a clean bowl, white cells rush in like tiny dots and surround it. They form a tight ring around the invader and break it apart. Once the threat is gone, a few cells stay behind in the bowl as guards.
Explaining immune response by grade level
Some foods like milk can make a few people feel sick. Their body thinks the food is bad. It sends tiny helpers in the blood to fight it. That is why they get a rash or a tummy ache.