viruses and other infectious agents have developed many ways to escape the immune system, but the...
TRANSCRIPT
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
An Evolutionary Arms Race
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Infection Immune system
Credits: Ahmed Sheriff, Deniz Zeisig, Susanne Bürgis, Alexandros Theodoridis, Tobias Strapatsas, Hans-Martin Jäck, Aaron Marshall
basic immunologyDGfI
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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
How does the body defend itself against these invaders?
With the help of the
Immune system
Influenza virus Salmonella bacterium
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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)
When the immune system errs...
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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
ALLERGYALLERGY
Why do some people´s immune systems give allergic reactions, but not others?
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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!
When the immune system errs...
AutoimmunityAutoimmunity
Know your immune system! What is it really?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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(I) Innate Immunity
Barriers
Blood proteins
Phagocytes
(II) Acquired immunity
B- and T-Cells
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Defence mechanisms against infectionsDefence mechanisms against infections
(I) Innate Immunity - Barriers(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 (I) Innate Immunity = immediate defence reactions
Phagocytes, also known as macrophages
Microbes become food!
Attract more phagocytes
Release messenger molecules that affect the whole body (Interleukins)
Fever, new formation of phagocytes, opening of local blood vessels
HELP
Proteins from the blood attach to microbes
marking of the microbes for phagocytes (eat me!)
direct destruction of microbes
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Characteristics of inflammation: Redness, swelling, pain, heat
Inflammation brings rapid assistance
A wound = a call to arms!A wound = a call to arms!
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 infectionsDefence mechanisms against infections
Ready to fight many pathogens
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(I) Innate Immunity
Barriers
Blood proteins
Phagocytes
(II) Acquired immunity
Activation of specific immune cells:
B- and T-Cells
Need to learn how to fight eachnew pathogen (and can rememberafterwards!)
(II) Aquired immunity - the Lymph System(II) Aquired immunity - the Lymph System
Tonsils
HeartThymus
Kidney
Appendix
Lymph nodes
SpleenPeyers Patches
Bone Marrow
• Thymus
• Bone Marrow
• Lymph nodes
• Spleen
• Tonsils
• Appendix
Lymph nodes
Adenoids
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(II) Aquired immunity = a custom-tailored defensive (II) Aquired immunity = a custom-tailored defensive strategystrategy
Initiation
Phagocytes and dendritic cells alert B and T cells
Activation!
ZZZ
Z
Who needs my
help?
ZZZZ
T
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T-cells get into the action T-cells get into the action
Activation of B cell Antibody production
Destruction of the infected cells
T-cell
Killer T-cell Helper T-cell
Asta la vista, baby!
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B-cells get into the actionB-cells get into the action
Interaction of B-cell and T-Helper cell in lymph node
B cell becomes a plasma cellAntibodes are produced to
neutralize the invader!
Finally you‘re here!
Here comes help!T
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Influenza Virus
Antibodies bind to surface projectionsneutralizing the virus
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Lock-and-Key Principle
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The immune system has a memory 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!!!
TB
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Y
Y Y
Y
BUT - Viruses routinely use small variations to evade immune memory!
Small variations in the Virus genes
Y
YY
Y
Small variations in the virus surface structure
Reduced protection by Antibody
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Bird cell
OR RARELY - Large change to completely escape immunity:
Y
YY
Y
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Large variations in the Virus genes occur in another species
Completely different virus surface structures
NO protection by Antibody - Bird flu pandemic!
Fast
Specific for type of microbe
Constant level of protection
Takes time to develop
Specific for exact microbe
Memory for strong protection in the future
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Defence mechanisms against infectionsDefence mechanisms against infections
(I) Innate Immunity
Barriers
Blood proteins
Phagocytes
(II) Acquired immunity
Activation of specific immune cells:
B- and T-Cells
What causes allergy?
B cell meets an Allergen and produces antibodies
-> WHY do B cells sometimes mistake Allergens for Pathogens?
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Pollen
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
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Allergy symptoms
Why do some people‘s immune systems give allergic reactions, but not others?
GenesEnvironmental exposure to allergensAir pollutionSmoking???
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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?
Questions
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We’re working on it!
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Your Questions?