Topic Three

How does the immune system respond to infectious diseases?

This topic explores how the immune system protects the body from infectious diseases through three lines of defence: mechanical barriers, inflammatory responses, and targeted immune responses. It explains the difference between non-specific (innate) and specific (adaptive) immunity.

LEARNING INTENTIONS

  • Understand how the immune system defends the body against infectious diseases.
  • Recognise and describe the three lines of defence used by the body.
  • Understand the difference between non-specific and specific immune responses. 

SUCCESS CRITERIA

  • Define and explain the immune system and its purpose in fighting infections.
  • Identify and categorise the three lines of defence as non-specific or specific. 
  • Describe the role of the lymphatic system and lymphocytes in targeted immune responses.

About the immune system

 The immune system is the body’s defence network, designed to protect against infectious organisms and harmful invaders. It works tirelessly to keep us healthy by identifying, targeting, and eliminating these threats. The immune system operates through three lines of defence (see below), each playing a crucial role in stopping infections. 

First Line of Defence

Physical and chemical barriers like skin, mucus and stomach acid block pathogens from entering the body. 

Second Line of Defence

Non-specific immunity kicks in when invaders breach these barriers, using white blood cells and inflammation to attack and eliminate threats. 

Third Line of Defence

Specific immunity targets known pathogens, creating antibodies and memory cells to respond faster and more effectively in the future. 

Real Life Example

 By understanding how the immune system works, we can see why measures like vaccinations are vital. Vaccines strengthen the immune system, preparing it to recognise and combat specific diseases like polio, which has been nearly eradicated through immunisation. In an interview with Prof. Robert Booy, polio survivor Gary Newton shares how vaccination transformed his life and why community immunity is essential. 

Pre-Learning Activity

Part 1:

Recap Questions from Topic 2:

1. What are the 4 main categories of pathogens?
2. What is an example of a disease caused by each?
3. How does it enter the body? 

Topics
Topic 3.2