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DGfI
basic immunology
An Evolutionary Arms Race
Immune system
Infection
Viruses and other infectious agents have
developed many ways to escape the immune system,
but the immune system also has a lot of clever
strategies
Credits Ahmed Sheriff, Deniz Zeisig, Susanne
Bürgis, Alexandros Theodoridis, Tobias
Strapatsas, Hans-Martin Jäck, Aaron Marshall
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Pandemic Spanish Flu 1918/1919
Estimated 40 Million dead
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Salmonella bacterium
How does the body defend itself against these
invaders?
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Our Immune System can also defend us against
cancer arising in the body
A T cell (orange) killing a cancer cell (mauve)
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• When the immune system errs...

ALLERGY
Allergy happens when the immune system mistakenly
defends against a microbe thats not really a
microbe pollen, house dust, cat hair, specific
foods A very widespread problem, and rising up
to 30 of the population in some developed
countries
Why do some peoples immune systems give
allergic reactions, but not others?
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When the immune system errs...
Autoimmunity

• Rheumatoid arthritis (joints)
• Inflammatory bowel disease (intestine)
• Type I diabetes (pancreas)
• Multiple sclerosis (brain and spinal cord)
• Systemic lupus erythrematosus (multiple tissues)

It is also important to know how we can turn an
over-active immune system OFF!
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Know your immune system! What is it really?
Consists of certain substances and cells in the
body, that each provide different kinds of
defenses against pathogens
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Defence mechanisms against infections
(II) Acquired immunity B- and T-Cells
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(I) Innate Immunity - Barriers
Skin Saliva Stomach acid Intestinal flora
Pathogens find ways to penetrate body barriers!
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(I) Innate Immunity immediate defence reactions
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A wound a call to arms!
Inflammation brings rapid assistance
Characteristics of inflammation Redness,
swelling, pain, heat
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Defence mechanisms against infections
(II) Acquired immunity Activation of specific
immune cells B- and T-Cells
Need to learn how to fight each new pathogen (and
can remember afterwards!)
Ready to fight many pathogens
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(II) Aquired immunity - the Lymph System
Adenoids
Tonsils
Thymus
Heart
Lymph nodes
Spleen
Kidney
Peyers Patches
Appendix
Lymph nodes
Bone Marrow
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(II) Aquired immunity a custom-tailored
defensive strategy
Activation!
Who needs my help?
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T-cells get into the action
T-cell
Killer T-cell
Helper T-cell
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B-cells get into the action
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Influenza Virus
Antibodies bind to surface projections neutralizi
ng the virus
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Lock-and-Key Principle
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The immune system has a memory
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BUT - Viruses routinely use small variations to
evade immune memory!
Small variations in the Virus genes
Small variations in the virus surface structure
Reduced protection by Antibody
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Y
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Y
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OR RARELY - Large change to completely escape
immunity
Large variations in the Virus genes occur in
another species
Completely different virus surface structures
NO protection by Antibody - Bird flu pandemic!
Bird cell
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Defence mechanisms against infections
(II) Acquired immunity Activation of specific
immune cells B- and T-Cells
Takes time to develop Specific for exact
microbe Memory for strong protection in the
future
Fast Specific for type of microbe Constant level
of protection
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What causes allergy?
Pollen
B cell meets an Allergen and produces
antibodies -gt WHY do B cells sometimes mistake
Allergens for Pathogens?
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Mast cells bind these antibodies on their surface
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When the loaded mast cells come into contact with
allergen they are activated and produce histamine
Histamine
Allergy symptoms
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Why do some peoples immune systems give allergic
reactions, but not others?
Genes Environmental exposure to allergens Air
pollution Smoking ???
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Questions
How can we reverse immune responses to
allergens? How do we turn off autoimmunity
without completely destroying the immune
system? Can we mobilize the immune system to
fight off cancer? How can we quickly mobilize
the immune system to fight new emerging
infectious diseases? SARS, bird flu How to
develop vaccines for chronic infections such as
HIV?
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Were working on it!
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Your Questions?