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An Evolutionary Arms Race

Day of. Immunology. 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.

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An Evolutionary Arms Race

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  1. Day of Immunology DGfI basicimmunology 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

  2. Day of Immunology

  3. Day of Immunology Pandemic: Spanish Flu 1918/1919 Estimated 40 Million dead

  4. Day of Immunology Infectious microbes are everywhere: Bacteria, viruses, fungi, parasites Influenza virus With the help of the Immune system Salmonella bacterium How does the body defend itself against these invaders?

  5. Day of Immunology Our Immune System can also defend us against cancer arising in the body A T cell (orange) killing a cancer cell (mauve)

  6. Day of Immunology 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 When the immune system errs... Why do some people´s immune systems give allergic reactions, but not others?

  7. Day of Immunology 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!

  8. Day of Immunology • The armed forces of the body: • White Blood Cells such as • B-cells and T-cells (Lymphocytes) • Phagocytes • Blood proteins • Antibodies 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

  9. Day of Immunology (I) Innate Immunity Barriers Blood proteins Phagocytes Defence mechanisms against infections (II) Acquired immunity B- and T-Cells

  10. Day of Immunology (I) Innate Immunity - Barriers Skin Saliva Stomach acid Intestinal flora Pathogens find ways to penetrate body barriers!

  11. Day of Immunology 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! • Attract more phagocytes • Release messenger molecules that affect the whole body(Interleukins)  Fever, new formation of phagocytes, opening of local blood vessels HELP (I) Innate Immunity = immediate defence reactions

  12. Day of Immunology The fight begins against growth and spreading of the pathogens : phagocytes are called in, wound healing is started A wound = a call to arms! Inflammation brings rapid assistance Characteristics of inflammation: Redness, swelling, pain, heat

  13. Day of Immunology (I) Innate Immunity Barriers Blood proteins Phagocytes 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

  14. Day of Immunology • Thymus • Bone Marrow • Lymph nodes • Spleen • Tonsils • Appendix (II) Aquired immunity - the Lymph System Adenoids Tonsils Thymus Heart Lymph nodes Spleen Kidney Peyers Patches Appendix Lymph nodes Bone Marrow

  15. Day of Immunology Initiation Phagocytes and dendritic cells alert B and T cells Z Z Z Z T Z Z Z Z (II) Aquired immunity = a custom-tailored defensive strategy Activation! Who needs my help?

  16. Day of Immunology Destruction of the infected cells Activation of B cell  Antibody production Asta la vista, baby! T-cells get into the action T-cell Killer T-cell Helper T-cell

  17. Day of Immunology Interaction of B-cell and T-Helper cell in lymph node Here comes help! Finally you‘re here! T B cell becomes a plasma cell Antibodes are produced to neutralize the invader! B-cells get into the action

  18. Day of Immunology Influenza Virus Antibodies bind to surface projections neutralizing the virus

  19. Day of Immunology Lock-and-Key Principle

  20. Day of Immunology ! 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 The immune system has a memory

  21. Day of Immunology Y Y Y Y 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 Y Y Y Y

  22. Day of Immunology Y Y Y Y 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

  23. Day of Immunology (I) Innate Immunity Barriers Blood proteins Phagocytes 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

  24. Day of Immunology What causes allergy? Pollen B cell meets an Allergen and produces antibodies -> WHY do B cells sometimes mistake Allergens for Pathogens?

  25. Day of Immunology Mast cells bind these antibodies on their surface

  26. Day of Immunology When the loaded mast cells come into contact with allergen they are activated and produce histamine Histamine Allergy symptoms

  27. Why do some people‘s immune systems give allergic reactions, but not others? Genes Environmental exposure to allergens Air pollution Smoking ???

  28. Day of Immunology ? 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?

  29. Day of Immunology We’re working on it!

  30. Day of Immunology ? Your Questions?

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