Immune System Vocabulary

4. When pathogens enter the body, multiply, and cause illness or symptoms.
6. A marker or substance on a pathogen that the immune system recognizes as foreign and dangerous.
7. Very small germs that are not alive on their own and must enter body cells to multiply and cause disease.
8. Cells in the blood that fight infection and protect the body from disease.
9. Tiny living organisms made of a single cell. Some are helpful, but others can cause illness.
11. The ability of the body to resist or fight off infection.
12. The body’s defense system that protects you from germs and diseases.
13. Harmful germs (like bacteria or viruses) that can make you sick.

1. A network of vessels, nodes, and organs that helps remove waste, fight infection, and return fluid (lymph) back to the bloodstream.
2. The body’s fast, natural first line of defense you are born with, such as skin, mucus, and certain white blood cells.
3. The body’s learned defense system that remembers specific germs and fights them better the next time you are exposed.
5. Special proteins made by white blood cells that attach to antigens to help destroy pathogens.
10. A clear fluid that carries white blood cells through the lymphatic system and helps remove waste and germs.