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DGfI
Day of
basic immunology
An Evolutionary Arms Race
Infection
Immune system
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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Infectious microbes are everywhere:
Bacteria, viruses, fungi, parasites
Influenza virus
Salmonella bacterium
How does the body defend itself against these invaders?
With the help of the
Immune system
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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 that’s
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 people´s 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
The armed forces of the body:
• White Blood Cells such as
B-cells and T-cells (Lymphocytes)
• Phagocytes
• Blood proteins
• Antibodies
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Defence mechanisms against infections
(I) Innate Immunity
Barriers
Blood proteins
Phagocytes
(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
Proteins from the blood attach to microbes
 marking of the microbes for phagocytes (eat me!)
 direct destruction of microbes
Phagocytes, also known as macrophages
 Microbes become food!
HELP
 Attract more phagocytes
 Release messenger molecules that affect the whole body
(Interleukins)
 Fever, new formation of phagocytes, opening of local blood vessels
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A wound = a call to arms!
Inflammation brings rapid assistance
Characteristics of inflammation: Redness, swelling,
pain, heat
The fight begins against growth and spreading of the pathogens :
phagocytes are called in, wound healing is started
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Defence mechanisms against infections
(I) Innate Immunity
(II) Acquired immunity
Barriers
Blood proteins
Phagocytes
Ready to fight many pathogens
Activation of specific
immune cells:
B- and T-Cells
Need to learn how to fight each
new pathogen (and can remember
afterwards!)
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(II) Aquired immunity - the Lymph System
Adenoids
Tonsils
Lymph nodes
Kidney
Thymus
Heart
Spleen
Peyers Patches
Appendix
• Thymus
• Bone Marrow
• Lymph nodes
• Spleen
• Tonsils
Lymph nodes
Bone Marrow
• Appendix
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(II) Aquired immunity = a custom-tailored defensive
strategy
Initiation
Phagocytes and dendritic cells alert B and T cells
Z
Z
Z Z
Z
T
Who
needs my
help?
ZZ
Z
Activation!
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T-cells get into the action
T-cell
Killer T-cell
Destruction of the infected cells
Asta la
vista,
baby!
Helper T-cell
Activation of B cell
 Antibody production
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B-cells get into the action
Interaction of B-cell and T-Helper cell in lymph node
T
Here
comes
help!
Finally
you‘re
here!
B cell becomes a plasma cell
Antibodes are produced to
neutralize the invader!
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Influenza Virus
Antibodies bind to
surface projections
neutralizing the virus
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Lock-and-Key Principle
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The immune system has a memory
! The immune system can learn !
Memory B- and T-cells can remember the invading microbe for years.
Therefore next time the same microbe is encountered, one can fight it off
faster and more effectively. Think vaccination!!!
T
B
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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
Y
Reduced protection by Antibody
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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
(I) Innate Immunity
(II) Acquired immunity
Barriers
Blood proteins
Phagocytes
Activation of specific
immune cells:
B- and T-Cells
Fast
Takes time to develop
Specific for type of microbe
Specific for exact microbe
Constant level of protection
Memory for strong protection
in the future
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What causes allergy?
Pollen
B cell meets an Allergen and produces antibodies
-> 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
Why do some people‘s 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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We’re working on it!
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Your Questions?