presentation to go along with the IB Biology HL topic of immune system (6.3 & 11.1)

1. The Immune System
Topics 6.3 and 11.1

2. Immunity
• Immunity
– The ability of the body to fight infection and/or foreign
invaders by producing antibodies or killing infected cells.
• Immune System
– The system in the body responsible for maintaining
homeostasis by recognizing harmful from non-harmful
organisms and produces an appropriate response.
• Highly specific recognition of foreign antigens
• Mechanisms for elimination of microbes bearing such
antigens
• A vast universe of distinct antigenic specifies
• Immunologic memory
• Tolerance of self-antigens

3. Key attributes of immune system
• 4 attributes that characterize the
immune system as a whole
– specificity
• antigen-antibody specificity
– diversity
• react to millions of antigens
– memory
• rapid 2° response
– ability to distinguish self vs. non-self
• maturation & training process to reduce auto-
immune disease

4. Foreign Invaders
• Called Pathogens
– Viruses, bacteria or
other living thing that
causes
disease/immune
response.
• Antigens
– Toxins that pathogens
produce that cause
harm to an organism.

5. Avenues of attack
• Points of entry
– digestive system
– respiratory system
– urogenital tract
– break in skin
• Routes of attack
– circulatory system
– lymph system

6. Parts of the Immune System
1. Blood - White Blood Cells in particular.
2. Lymph nodes
3. Thymus Gland – Produces T Lymphocytes
4. Bone Marrow – Produces B Lymphocytes

7. Production & transport of leukocytes
Lymph system Traps foreign invaders
lymph vessels
(intertwined amongst blood vessels)
lymph node

8. Lines of Defense

9. How does the body fight infection/foreign invaders?
First Line of Defense – The Skin
• Provides Physical and Chemical barriers
• Physical – hard to penetrate, made of indigestible keratin
• Chemical – tears, sweat

10. 1st line: Chemical barriers on epithelium
Skin & mucous membrane secretions
– Sweat -pH 3-5
– Tears- washing action, lysozyme
– Mucus- traps microbes
– Saliva- anti-bacterial = “lick your wounds”
– Stomach acid- pH 2
– Anti-microbial proteins
• lysozyme enzyme
– digests bacterial cell walls

11. 2nd Line – Nonspecific Immune Response
These are defenses the body uses no matter what the invader
may be. These defenses include:
– Phagocytosis – done by Macrophages
– Natural Cell Killers
– Inflammation - caused by release of Histamine from
leukocytes
– Fever – caused by histamines. The fever (high temp) kills
invaders by denaturing their proteins.

12. 2nd line: Internal, broad range patrol
• Innate, general defense leukocytes
– rapid response
• Patrolling cells & proteins
– attack invaders that penetrate
body’s outer
barriers
• leukocytes
– phagocytic white blood cells
• complement system
– anti-microbial proteins
• inflammatory response

13. Leukocytes: Phagocytic white blood cells (WBCs)
• Attracted by chemical
signals released by damaged cells
– enter infected tissue, engulf & ingest microbes
• lysosomes
• Neutrophils
– most abundant WBC (~70%)
– ~ 3 day lifespan
• Macrophages
– “big eater”, long-lived
• Natural Killer Cells
– destroy virus-infected cells
& cancer cells

14. Phagocytes
macrophage yeast

15. Destroying cells gone bad!
• Natural Killer Cells perforate cells
– release perforin protein
– insert into membrane of target cell
– forms pore allowing fluid to
flow into cell natural killer cell vesicle
– cell ruptures (lysis)
• apoptosis perforin
cell
membrane
perforin cell
membrane
punctures
cell membrane virus-infected cell

16. Anti-microbial proteins
• Complement system
– ~20 proteins circulating in blood plasma
– attack bacterial & fungal cells
• form a membrane attack complex
• perforate target cell
extracellular fluid
• apoptosis
complement proteins
form cellular lesion
plasma membrane of
invading microbe complement proteins
bacterial cell

18. Inflammatory response 1
• Damage to tissue triggers local
non-specific inflammatory
response
– release histamines & prostaglandins
– capillaries dilate,
more permeable (leaky)
• increase blood supply
• delivers WBC, RBC, platelets, clotting
factors
• fight pathogens
• clot formation
• accounts for swelling, redness & heat
of inflammation & infection

19. Fever
• When a local response is not enough
– systemic response to infection
– activated macrophages release interleukin-1 (IL-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

20. The Inflammatory Response
• 1- Tissue injury; release of chemical signals~
• histamine (basophils/mast cells): causes Step 2...
• prostaglandins: increases blood flow & vessel permeability
• 2/3- Dilation and increased permeability of capillary~
• chemokines: secreted by blood vessel endothelial cells
mediates phagocytotic migration of WBCs
• 4- Phagocytosis of pathogens~
• fever & pyrogens: leukocyte-released molecules increase body
temperature

21. 3rd line: Acquired (active) Immunity
• Specific defense
– lymphocytes
• B lymphocytes (B cells)
• T lymphocytes (T cells)
– antibodies
• immunoglobulins
• Responds to…
– antigens
• specific pathogens
• specific toxins
• abnormal body cells
(cancer)

22. 3rd Line – Specific Immune Response
This is a specific response to a specific
pathogen/antigen.
The response involves the creation of Antibodies.

23. Antibodies
• Y-shaped protein
molecule.
• Made up of variable and
constant regions.
• Made up of Heavy and
Light chains.
• Produced by B-
Lymphocytes
• Function: Recognize
antigens, bind to and
deactivate them.
– Note: Variable region
recognizes the anitgens.

24. Antigens- recognition of invaders
• Antigens
– proteins that serve as cellular name tags
• foreign antigens cause response from WBCs
– viruses, bacteria, protozoa, parasitic worms, fungi, toxins
– non-pathogens: pollen & transplanted tissue
• B cells & T cells respond to different antigens
– B cells recognize intact antigens
• pathogens in blood & lymph
– T cells recognize antigen fragments
• pathogens which have already infected cells
“self” “foreign”

25. How an antibody operates/works?
Deactivation of a bacterium by an antibody.

26. How are cells tagged with antigens?
• Major histocompatibility (MHC) proteins
– antigen glycoproteins
– MHC I – on all nucleated cells
– MHC II – on macrophages, B-Ly, activated T-Ly
• MHC proteins constantly carry bits of cellular
material from the cytosol to the cell surface
– “snapshot” of what is going on inside cell
– give the surface of cells a unique label or “fingerprint”
T cell
MHC proteins
displaying self-antigens

27. The Pathway of Specific Immune Response
Step 1
Pathogens eaten by Macrophage
Step 2
Displays portion of Pathogen
on surface
Step 3
Pathogens
Helper-T cell recognizes
Pathogen

28. Activates Cytotoxic Activates B- Cell
T- Cell
Memory B-Cell
Memory T-Cell
Antibodies
Kills Infected Cells

29. Cellular Immunity vs. Antibody Immunity
Cellular Immunity Antibody or Humoral Immunity
• Carried out by T-Cells • Carried out by B-cells
• Infected cells are killed by • Antibodies are produced
Cytotoxic T –Cells. and dumped into blood
stream.
• Antibodies bind to
antigens and deactivate
them.

30. Immune Response Explained
1. Antigen infects cells.
2. Macrophage ingests antigen and displays portion on its surface.
3. Helper T- Cell recognizes antigen on the surface of the
macrophage and becomes active.
4. Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.
5. Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory
T – Cells.
6. Active Cytotoxic T-Cells kill infected cells.
7. At the same time, B-Cells divide into Plasma Cells and Memory
B- Cells.
8. Plasma cells produce antibodies that deactivate pathogen.
9. Memory T and Memory B cells remain in the body to speed up the
response if the same antigen reappears.
10. Supressor T-Cells stop the immune response when all antigens
have been destroyed.

31. Immune Response Summary
Displays copy of antigen
on surface of cell
Antigen
Macrophage
Helper T - Cell Antibody Immunity
Cellular Immunity
Active Cytotoxic T-Cell Active B - Cell
Kills Infected Cells Memory T- Cell Plasma Cell Memory B-Cell
Antibodies
Deactivates Antigens

32. Primary .vs. Secondary Immune Response
• Primary Immune Response
– This is a response to an invader the 1st time the
invader infects the body.
• No measurable immune response for first few days.
• Next 10 – 15 days antibody production grows steadily
• Secondary Immune Response
– A more rapid response to an invader the 2nd time it
invades the body.
• Antibody production increases dramatically and in a much
shorter time period..

33. Primary .vs. Secondary Immune Response

34. Induction of Immune Responses
• Primary immune response: lymphocyte proliferation and
differentiation the 1st time the body is exposed to an antigen
• Plasma cells: antibody-producing effector B-cells
• Secondary immune response: immune response if the individual
is exposed to the same antigen at some later time~ Immunological
memory

35. Passive vs. Active Immunity
1. Active Immunity
This is immunity where the body is “actively” producing antibodies
to fight infection.
Ex: You have a throat infection and you are actively creating
antibodies to fight it.
Vaccination: An injection of a weakened strain of an
infectious microbe (pathogen) that causes the body to
undergo active immunity (produce antibodies).
1. Passive Immunity
This is immunity where antibodies are given to a
person from the blood of another person or animal.
This immunity only lasts for a short period of time.
ex: Breastfeeding mothers pass antibodies to their
children through the milk.

36. Autoimmune Disease
• Autoimmune diseases are diseases where the immune
system begins to attack itself.
– Ex:
• Rheumatoid Arthritis – crippling disease of the
joints.
• Lupus – disease of blood and organs.
• Multiple Sclerosis – disease of nervous system
• Cause(s): unknown
• Cures/Treatments: No known cures.

37. Allergies
Allergy
- An exaggerated response by the immune system to an allergen.
Allergen: a normally harmless substance that causes an allergic
reaction.
ex: dust, pollen, mould, food, insect stings
Types of Allergic reactions
There are two types of allergic reactions.
a. Immediate – occurs within seconds and normally lasts for about
30 mins.
b. Delayed – takes longer to react and can last for a much longer
time.

38. What happens during an allergic reaction?
• During an allergic reaction antibodies cause histamines to be
released from certain cells.
Histamines cause:
a. Swelling of tissues
b. Release of fluids (runny noses and eyes)
c. muscle spasms (some cases)
Anaphylaxis or anaphylactic shock:
This is the sudden and severe allergic reaction to a substance that
can cause death.
Treatments for Allergies
1. Avoidance of material – especially food.
2. Epinephrine – “epi – pen”
3. Antihistamines -- benadryl

39. Abnormal immune function
• Allergies (anaphylactic shock): hypersensitive responses to environmental
antigens (allergens); causes dilation and blood vessel permeability
(antihistamines); epinephrine
• Autoimmune disease: multiple sclerosis, lupus, rheumatoid arthritis,
insulin-dependent diabetes mellitus
• Immunodeficiency disease: SCIDS (bubble-boy); A.I.D.S.

40. HIV & AIDS
• Human Immunodeficiency Virus
– virus infects helper T cells
– helper T cells don’t activate rest of immune
system: T cells & B cells
• also destroy T cells
• Acquired ImmunoDeficiency Syndrome
– infections by opportunistic
diseases
– death usually from other
infections
• pneumonia, cancer

41. HIV
• HIV is a virus that specifically attacks the
lymphocytes.
• This means the number of lymphocytes
decreases.
• Less antibodies are made.
• Predict the consequences…

42. HIV Progression

43. Transmission of HIV
• Infected blood – blood transfusions,
sharing needles,
• Infected semen and vaginal mucus –
unprotected sex
• Infected mother’s milk – low risk
• Infected saliva – almost zero risk

44. AIDS
• Caused by the HIV virus that selectively
infects the immune system leaving the
body open to infection by removing the
specific immunity.

45. Social implications of AIDS
• Cases of AIDS are not evenly distributed in the
world, for example there are severe problems in
Africa (some populations with 30% of their
people are infected).
• What cultural and economic reasons are there
for differences in the prevalence of AIDS?
• Is there a moral obligation of those with the
technology and the wealth to help others lacking
these things in the fight against AIDS?