1. Fighting the Enemy Within!
phagocytic leukocyte
Fighting the Enemy Within!
Immune System
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: INNATE barriers
broad, external defense structures
“walls & moats”
2nd line: INNATE patrols
broad, internal defense cells
“patrolling soldiers”
3rd line: Adaptive Immunity
specific pathogens targeted
“elite trained units”
Bacteria & insects inherit resistance.
Vertebrates acquire immunity.

4. 1st line: Examples Barrier Traps Elimination Unfavorable pH
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: Examples Cells attacking ALL invaders leukocytes
bacteria
Cells attacking ALL invaders
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
Pathogen
Splinter
Movement
of fluid
Signaling
molecules
Macro-
phage
Mast
cell
Capillary
Phagocytosis
Red blood cells
Neutrophil
Figure Major events in a local inflammatory response (step 3) 1
Histamines and cytokines
released. Capillaries dilate. 2
Antimicrobial
peptides enter tissue.
Neutrophils are
recruited. 3
Neutrophils
digest pathogens
and cell debris.
Tissue heals.

7. Fevers System-wide response to infection
Activated macrophages release interleukin-1
triggers hypothalamus in brain to readjust body thermostat to raise body temperature
Is this a positive or negative feedback response?
higher temperature helps defense
inhibits bacterial growth
causes liver & spleen to store iron, reducing blood iron levels
bacteria need large amounts of iron to grow
Septic Shock – inflammatory reaction out of control
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 Immunity
B cell
Specific pathogens are recognized and attacked
“True Immune System”
WBC’s – Lymphocytes:
B cells
T cells
Two Processes:
Humoral Immunity
Cell Mediated Immunity
T cell

9. How Are Cells/Pathogens Recognized?
Surface protein markers – ANTIGENS
Antigens can elicit a response from lymphocytes
“self” antigens
no response from WBCs
Class I MHC – major histocompatibility complex protein markers on cell membrane of ALL cells

10. “foreign” antigens response from WBCs
pathogens: viruses, bacteria, protozoa, worms, fungi, toxins
non-pathogens: cancer cells, transplanted tissue, pollen, food, chemicals

11. Humoral Response
Attacks foreign antigens in blood or lymph
Antibody proteins are produced to attack specific antigen markers on pathogens
B Cells types:
plasma cells
immediate production of antibodies
rapid response, short term release
memory cells
continued circulation in body
long term immunity

13. What do antibodies do to invaders?

14. 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

15. Cell-Mediated Response
Killer T cell binds to infected cells
Secretes perforin protein causing apoptosis or lysis of infected cell
Creates memory killer-T’s for further exposures

16. How Do Helper T Cells Work?
Binds to an Antigen Presenting Cells (APC) displaying foreign antigen on cell membrane
Class II MHC markers
Activates itself with cytokines and clones into 1000’s
Cloned Helper T’s search for specific B Cell and Killer T for the same pathogen
MHC proteins displaying foreign antigens
infected cell
TH cell
WANTED
Helper T cell with antigen receptors

17. Helper T’s Role in Immunity
“I am going to clone myself.”

18. What is the correct sequence in which the following occur during a primary humoral immune response?
B cell activation
helper T cell activation
plasma cell differentiation and proliferation
antibody secretion
presentation of antigen on class II MHC proteins
5, 2, 1, 4, 3 d) 4, 5, 3, 1, 2
4, 5, 2, 1, 3 e) 5, 2, 1, 3, 4
5, 1, 2, 3, 4 18

19. What is the correct sequence in which the following occur during a primary humoral immune response?
B cell activation
helper T cell activation
plasma cell differentiation and proliferation
antibody secretion
presentation of antigen on class II MHC proteins
5, 2, 1, 4, 3 d) 4, 5, 3, 1, 2
4, 5, 2, 1, 3 e) 5, 2, 1, 3, 4
5, 1, 2, 3, 4 19

20. 2 Types: ACTIVE and PASSIVE
What is Immunity?
2 Types: ACTIVE and PASSIVE

21. Active Immunity Must get exposed to the pathogen! Naturally – get sick
Artificially – get a vaccination
Both methods cause memory cells to be made for future exposures.
How long does first exposure typically take to feel better?
Why was the 2nd exposure so short in duration?
What determines whether or not you are immune?

22. Primary Immune Response with B and T cell activation:

24. 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

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

26. 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, food
1st exposure you are not allergic. Allergy is confirmed after subsequent exposures
Anaphylaxis – most severe reaction

28. Overview of Immune Systems
Figure 43.2
Pathogens
(such as bacteria,
fungi, and viruses)
Overview of
Immune Systems
INNATE IMMUNITY
(all animals)
Barrier defenses:
Skin
Mucous membranes
Secretions
Recognition of traits
shared by broad
ranges of pathogens,
using a small set of
receptors
Internal defenses:
Phagocytic cells
Natural killer cells
Antimicrobial proteins
Inflammatory response
Rapid response
Figure 43.2 Overview of animal immunity
ADAPTIVE IMMUNITY
(vertebrates only)
Humoral response:
Antibodies defend against
infection in body fluids.
Recognition of traits
specific to particular
pathogens, using a
vast array of receptors
Cell-mediated response:
Cytotoxic cells defend
against infection in body
cells.
Slower response