1. Continue reading Chapter 13 and Supp 14
Immune System
Continue reading Chapter 13 and Supp 14

2. Learning objectives
What is a pathogen? What kinds of life forms can be pathogens?
What is meant by “3 lines of defense” against pathogens?
Explain how the first line of defense prevents entry of pathogens. How does each work?
Explain how the 2nd line is a general system that is always ready, to respond to general threats.
Explain how the 3rd line is very specific to the threat, but takes time to respond.
How are infectious diseases spread?

3. Pathogens
Virus
Bacteria
Fungi
Helminths
Protozoa
Ectoparasites

7. 2nd Line of Defense: Innate Immune system
Rapid response to infection
Increased blood flow to infection site
Neutrophils and Macrophages (types of WBC)
Engulf pathogens
Natural killer cells (WBC)
Kill virus-infected and cancer cells
WBCs release proteins that attract more WBCs

8. Figure 29.1
Sensors of Microbial Infection

10. Pathogens have ANTIGENS that identify them as ‘non-self’

11. 3rd Line of Defense: Acquired immunity
Specificity: B and T cells (WBC) make receptors for one type of antigen
Diversity: Collectively, B and T cells have receptors for at least a billion threats
Memory: Some B and T cells held in reserve for future infections

12. Figure 29.8
Prepared for an Invasion

13. Antigen is recognized B and T cells divide rapidly
Effector cells go for immediate attack
Memory cells set aside for future threats
B and T cells produce lots of antibodies
Mark invaders as non-self and allow other cells to destroy them.

14. Memory cells Live long after infection heals
Keep body ‘primed’ to fight infection
Can mount very quick response
Kill pathogens before they have a chance to reproduce much.