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
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
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
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
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..
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
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…
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?
Editor's Notes
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.
Major Histocompatability Complex (MHC): body cell surface antigens coded by a family of genes Class I MHC molecules: found on all nucleated cells Class II MHC molecules: found on macrophages, B cells, and activated T cells
----- Meeting Notes (11/25/12 20:21) -----
AIDS: Acquired Immuno deficiency syndrome . Acquired relates the infectious nature of AIDS through the transmission of the HIV virus. Immuno deficient relates to the way diseases cannot be resisted. Syndrome relates to the variation in the way the disease manifest itself. People who develop AIDS can be a affected by quite different set of diseases.