1. Lymphatic System
Lymphatic system: network of lymphatic vessels and organs
Returns tissue fluid to the circulatory system
Fights infections

2. Lymphatic System Lymph nodes key sites for fighting infection
Packed with lymphocytes and macrophages

3. Immune System: Nonspecific Defense
Body’s first lines of defense against infection
skin, mucous membrane, enzymes, tears, acids, proteins, macrophages
Nonspecific: do not distinguish one infectious microbe from another

4. Immune System: Nonspecific Defense
Macrophages wander interstitial fluid
“eat” any bacteria and virus-infected cells they encounter

5. Immune System: Specific Defense
Specific Response: immune systems responds to foreign molecules - antigens
Pathogen: foreign invader
Antigen: piece of pathogen that our white blood cells recognize

6. Immune System: Specific Defense
Two kinds of lymphocytes
B cells - secrete antibodies, wander fluid
T cells attack cells infected with pathogens
Antigen enters the body, it activates only lymphocytes with matching receptors

7. Immune System: Primary and Secondary Response

8. Immune System: B Cells Primary vs Secondary Response
B cell differentiates into:
Effector cell (plasma cell) – makes antibodies
Memory cell: remembers for next time

9. Immune System: Active vs Passive Immunity
Active: when you’re cells made antibodies / longterm
vaccination
Passive: when given antibodies
No memory cells made
Short term, ex breast feeding

10. Immune System: T Cells T cells : when cells have been attacked
Helper T cells and killer T cells
Helper T cells
recognize attacked cell and divide
Killer T cells
destroy infected cell so virus can’t multiply

11. Immune System: Disorders
Autoimmune diseases
System turns against the body’s own molecules
Immunodeficiency diseases
Immune system compromised
Ex. AIDS virus attacks helper T Cells
Physical and emotional stress may weaken the immune system