Pathogens & the Immune System
Explain how pathogens (bacteria, viruses, and fungi) cause disease and describe how the immune system responds, including the roles of white blood cells (phagocytosis, antibody production) and the concept of immunity
What a learner can do afterwards
- Distinguishes between bacteria, viruses, and fungi as pathogens with examples of each
- Explains two ways white blood cells destroy pathogens (engulfing and antibodies)
- Explains how vaccination works and why it prevents disease
- Explains the difference between being infected and being ill
1 · Read
A pathogen is a germ that causes disease. There are three main kinds you will meet here: bacteria, viruses, and fungi. Bacteria are single cells that carry out every life process alone. Strep throat comes from bacteria. The flu comes from a virus. Athlete's foot comes from a fungus. All three make you feel sick, but they are different types of germs, and that is why the same medicine does not work on all of them. Many vaccines use a weakened or dead piece of a pathogen that trains your defense against that exact germ.
Your body fights pathogens with white blood cells. Some white blood cells engulf a pathogen, swallowing it whole and breaking it down. Other white blood cells make antibodies, proteins shaped to lock onto one specific pathogen and mark it so it can be destroyed.
Many vaccines use a weakened or dead piece of a pathogen. It cannot give you the disease it protects against, but it lets your white blood cells practice making antibodies for that germ early, so your body is ready if the real one ever shows up.
Mia catches a cold virus on Monday. For two days her immune system fights it before she has any symptoms, so she is infected but not ill yet. On Wednesday her nose starts running and she coughs. Now she is infected and ill.
Bacteria, viruses, and fungi are different pathogens, white blood cells fight them by engulfing them or making antibodies, and a vaccine trains that defense before you get sick.
2 · Watch
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Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.