1. 3.1 The Immune System
Chapter 3 notes

2. The immune system
Pathogen – a disease causing organism or substance

3. Lines of defense Immune system helps keep your body safe
1. First line of defense
Skin and the linings of all internal body systems acts as a physical barrier 
Sweat and oil on your skin prevents some pathogens from growing 

4. Lines of Defense Acidic gastric juices destroy most pathogens
Mucous and cilia prevent pathogens from entering your respiratory system

5. Lines of defense 2. Second line of defense
a. Innate immune response – quick and general (against anything foreign)
Flow of fluid, cells and dissolved substances from the blood to the site of infection ... causes a fever, swelling and redness (inflammation)
Increase in types of white blood cells called phagocytes which swallow invader cells

6. Lines of Defense
b. Acquired immune response – attack on a specific pathogen (antigen – non living particle or substance)
B cells recognize antigens present in the body and produce antibodies to fight them (prevents the pathogen from infecting body cells or mark it for destruction by other white blood cells) 
T cells like helper T cells activate B cells; others called killer T cells work independently and directly destroy antigens or pathogens
Vaccines give you active immunity...they tell your body which antibodies were used to attack a pathogen that has infected it before

7. Immune system (4 steps)