1. Immune System phagocytic leukocyte Big Questions:
What is the purpose of a immune system?
How does the immune system function?
Why do animals have a more developed immune system?

2. Immune Systems Highly developed in mammals Two types of immunity:
Innate immunity (nonspecific)
Adaptive immunity (specific)
What about other organisms?
Lymphatic System: Production & transport of leukocytes (WBC)
Traps foreign invaders

3. Bacteria & insects inherit resistance. Vertebrates acquire immunity.
Lines of defense
1st line: Non-specific barriers
broad, external defense
“walls & moats”
skin & mucous membranes
2nd line: Non-specific patrols
broad, internal defense
“patrolling soldiers”
leukocytes = phagocytic WBC
3rd line: True immune system
specific, adaptive immunity
“elite trained units”
lymphocytes & antibodies
B cells & T cells
Bacteria & insects inherit resistance.
Vertebrates acquire immunity.

4. 1st line: Non-specific External defense
Barrier
skin
Traps
mucous membranes, cilia, hair, earwax
Elimination
coughing, sneezing, urination, diarrhea
Unfavorable pH
stomach acid, sweat, saliva, urine
Lysozyme enzyme
digests bacterial cell walls
tears, sweat
Lining of trachea: ciliated cells & mucus secreting cells

5. 2nd line: Non-specific patrolling cells
bacteria
Patrolling cells & proteins
attack pathogens, but don’t “remember” for next time
leukocytes
phagocytic white blood cells
macrophages, neutrophils (…pus), natural killer cells
complement system
proteins that destroy cells
inflammatory response
increase in body temp.
increase capillary permeability
attract macrophages
macrophage
yeast

6. Inflammatory response
chemotaxis

7. Fever When a local response is not enough
system-wide response to infection
activated macrophages release interleukin-1
triggers hypothalamus in brain to readjust body thermostat to raise body temperature
higher temperature helps defense
inhibits bacterial growth
stimulates phagocytosis
speeds up repair of tissues
causes liver & spleen to store iron, reducing blood iron levels
bacteria need large amounts of iron to grow
Certain bacterial infections can induce an overwhelming systemic inflammatory response leading to a condition known as septic shock.
Characterized by high fever and low blood pressure, septic shock is the most common cause of death in U.S. critical care units.
Clearly, while local inflammation is an essential step toward healing, widespread inflammation can be devastating.

8. 3rd line: Adaptive (active) Immunity
Specific defense with memory
lymphocytes
B cells - humoral response
T cells – cell mediated response
They respond to…
antigens
cellular name tags
specific pathogens
specific toxins
abnormal body cells (cancer)
B cell

9. B cells Involved in HUMORAL RESPONSE
Attacks foreign antigens in blood or lymph
Produce specific antibodies against specific antigens
Types of B cells
plasma cells
immediate production of antibodies
rapid response, short term release
memory cells
continued circulation in body
long term immunity

10. What do antibodies do to invaders?

11. Humoral Immune Response
Helper T cells can activate B cells directly.

12. T cells Involved in CELL MEDIATED RESPONSE
Attack, learn & remember pathogens hiding in infected cells
recognize antigen fragments
also defend against “non-self” body cells
cancer & transplant cells
Types of T cells
helper T cells
alerts rest of immune system
killer (cytotoxic) T cells
attack infected body cells
memory T cells
long term immunity
T cell attacking cancer cell

13. How do T cells know a cell is infected?
Infected cells digest some pathogens
MHC proteins carry pieces to cell surface
foreign antigens now on cell membrane
called Antigen Presenting Cell (APC)
macrophages can also serve as APC
tested by Helper T cells
MHC proteins displaying foreign antigens
infected cell
TH cell
WANTED
T cell with antigen receptors

14. Cell-Mediated Response
Cytotoxic T cells destroy infected body cells or cancer cells
activated by Helper T
binds to MHC of APC
secretes perforin protein causing apoptosis or lysis of infected cell
Creates memory killer-T’s for further exposures

15. Active Immunity Get exposed to pathogen! Naturally – get sick
Artificially – get a vaccination
Both methods cause memory cells to be made for future exposures.
Rapid response to second exposure. You don’t even know you were exposed!

16. Passive immunity (antibodies not immune cells)
Naturally
obtaining antibodies from mother
antibodies pass from mother to baby across placenta or in mother’s milk
critical role of breastfeeding in infant health
Artificially
injection of antibodies
Ex: anti-venom serum
short-term immunity

17. HIV & AIDS Human Immunodeficiency Virus
virus infects helper T cells
AIDS: Acquired ImmunoDeficiency Syndrome
infections and death by opportunistic diseases
pneumonia, cancers
HIV infected T cell

19. Immune system malfunctions
Auto-immune diseases
immune system attacks own molecules & cells
rheumatoid arthritis
Diabetes
multiple sclerosis
Allergies
makes wrong antibody for foreign antigen
allergens = proteins on pollen, dust mites, in animal saliva
1st exposure you are not allergic. Allergy is confirmed after subsequent exposures