1. Immune System Immune System Overview Influenza Infection
phagocytic leukocyte

2. Immune Systems Highly developed in mammals Two types of immunity:
Innate immunity (nonspecific)
Acquired 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, acquired 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
attack pathogens, but don’t “remember” for next time
leukocytes
phagocytic white blood cells
macrophages, neutrophils, natural killer cells, dendritic cells
Antimicrobial proteins
Complement system
Interferons
inflammatory response
increase in body temp.
increase capillary permeability
attract macrophages/neutrophils
macrophage
yeast

6. Inflammatory response
Histamine and cytokines increase blood flow to damaged site, making it look red and puffy = INFLAMMED!

7. 3rd line: Acquired (active) Immunity
Specific defense with memory
lymphocytes
B cells - humoral response
T cells – cell mediated response
They respond to…
Antigens!
B cell

8. 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

9. How are invaders recognized?
Antigens - cellular name tag proteins
“self” antigens
no response from WBCs
Major Histocompatibility Complex – MHC
Protein used by all cells for recognition
“foreign” antigens
response from WBCs
pathogens: viruses, bacteria, protozoa, parasitic worms, fungi, toxins
non-pathogens: cancer cells, transplanted tissue, pollen
Mature lymphocytes are tested to make sure they can distinguish self vs. non-self
“self”
“foreign”

10. Humoral Immune Response
In the diagram above a B cell is being activated by a T helper cell. This B cell will make plasma cells and memory B cells that will secrete antibodies to fight the current and future infections.

11. What do antibodies do to invaders?
Antibodies in Action

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
cytotoxic (killer) 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
Class I MHC proteins carry pieces of foreign cell to surface
foreign antigens now on cell membrane
called Antigen Presenting Cell (APC)
Helper T cell becomes active

14. Cell-Mediated Response
Activation of Helper T cell results in activation of Cytotoxic T cells (as well as B cells)
Cytotoxic T cells destroy infected body cells or cancer cells (look for Class I MHC)
Cytotoxic (killer) T cells secrete perforin protein causing apoptosis or lysis of infected cell

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

18. 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