1. Immune System Primary Function: To protect your body from pathogens.
Pathogens: Bacteria, viruses, fungus, or proteins that causes illness.
Spleen: stores lymphocytes and filters blood
Thymus: where T cells mature
Bone marrow: where blood cells are formed

2. Types of Immunity
Innate Immunity: - present before exposure to pathogens - is nonspecific
Acquired Immunity:
- develops after exposure to pathogens
- is very specific

3. Innate Immunity: External
Skin
- physical barrier that prevents entry of pathogens - secretions from the skin cause it to be acidic enough to prevent colonization of many pathogens

4. Innate Immunity: External
Mucous membranes
- Produce mucus, a fluid that traps pathogens
- Can contain enzymes like lysozyme that digest the cell walls of many pathogens

5. Innate Immunity: External
Cilia
- In the trachea, ciliated epithelial cells sweep upward, preventing the microbes from entering the lungs
Figure 43.3
10m

6. Innate Immunity: Internal
Phagocytic cells: attach to their prey using surface receptors and engulf them (endocytosis), forming a vacuole that fuses with a lysosome.
Macrophages are a type of phagocytic cell.

7. Innate Immunity: Internal
Natural Killer cells: Attack virus-infected cells and cancer cells. Cause apoptosis (cell death) in the cells they attack.

8. Innate Immunity: Internal
Inflammatory Response: injured cells release chemicals (histamines) that cause phagocytic cells to gather at the site.
Pathogen
Pin
Macrophage
Chemical signals
Capillary
Phagocytic cells
Red blood cell
Blood
clotting
elements
Blood clot
Phagocytosis
Fluid, antimicrobial proteins,
and clotting elements move
from the blood to the site.
Clotting begins. 2
Chemical signals released
by activated macrophages
and mast cells at the injury
site cause nearby capillaries
to widen and become more
permeable. 1
Chemokines released by various
kinds of cells attract more
phagocytic cells from the blood
to the injury site. 3
Neutrophils and macrophages
phagocytose pathogens and
cell debris at the site, and the
tissue heals. 4

9. Acquired Immunity
Antibodies: Proteins that recognize foreign molecules and mark them for destruction.

10. Acquired Immunity
B cells and T cells: - Circulate in the blood - Made in bone marrow - B cells produce antibodies - T cells attack pathogens

11. Acquired Immunity
Primary Response: B or T cells recognize the pathogen and reproduce. This creates many new cells, including memory cells.

12. Antibody concentration
Acquired Immunity
Secondary Response: Memory cells cause a faster, more efficient response to a pathogen
Antibody concentration
(arbitrary units)
104
103
102
101
100 7 14 21 28 35 42 49 56
Time (days)
Figure 43.13
Antibodies
to A
to B
Primary
response to
antigen A
produces anti-
bodies to A 2
Day 1: First
exposure to 1
Day 28:
Second exposure
to antigen A; first
antigen B 3
Secondary response to anti-
gen A produces antibodies
to A; primary response to anti-
gen B produces antibodies to B 4

13. Allergies
Allergies overly sensitive response by your immune system to a molecule (allergens) Cause: Cells in your immune system release histamines that cause an inflammatory response
Figure 43.20 1 2 3
Allergen
IgE
Histamine
Granule
Mast cell

14. Infectious Diseases
Any disease caused by “germs” that can be spread from one person to another. Germs include viruses, bacteria, and fungi.

15. Infectious Diseases: Whooping cough
Cause: Bacterial (Bordetella pertussis) 
Symptoms: Severe coughing fits that can cause fractured ribs, fainting, artery tears
Spread: Direct contact with mucus from the nose/throat of infected individuals
Prevention: Vaccine

16. Infectious Diseases: HIV/AIDS
Cause: Viral Symptoms: Initially, few, if any. May have flu-like symptoms. Over time, immune system is weakened because T cells are killed. Spread: Contact with bodily fluids Prevention: Avoid body fluids from infected individuals

17. Vaccines Improve your immune systems ability to fight off a pathogen.
Include a weakened or killed form of the pathogen or part of a pathogen.
Stimulates the immune system to recognize the pathogen and create memory cells.

18. Infectious Diseases: Strep Throat
Cause: Bacterial Symptoms: Fever, sore throat with white patches Spread: Airborne (saliva or nasal secretions) Prevention: Avoid contact with infected individuals, wash hands, keep hands away from face