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Life ScienceGrade 7-9

Immune System Answer Key

Learn how the body defends itself against pathogens using the immune system.

Looking for Immune System answers? This complete answer key provides verified solutions for all student exploration activities and assessment questions in the ExploreLearning Immune System Gizmo.

100% Free • Step-by-step explanations • Perfect for homework help • Covers all activities • Updated for 2026

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Lines of Defense

Q1.What's the first line of defense?

Answer

Physical barriers like skin, mucus, and cilia that stop pathogens from entering the body.

Q2.What's the second line of defense?

Answer

Non-specific immune responses like fever, inflammation, and white blood cells that attack any invader.

Q3.What's the third line of defense?

Answer

The specific immune response - antibodies and memory cells that target specific pathogens.

Antibodies and Vaccines

Q4.What's an antibody?

Q5.How do vaccines work?

Q6.What's an antigen?

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