2. 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 Day of Immunology Infection Immune system Credits: Ahmed Sheriff, Deniz Zeisig, Susanne Bürgis, Alexandros Theodoridis, Tobias Strapatsas, Hans-Martin Jäck, Aaron Marshall basic immunology DGfI

3. Day of Immunology

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

5. 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 Day of Immunology

6. 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)

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

8. Day of Immunology  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... Autoimmunity

9. 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 Day of Immunology

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

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

12. (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 Day of Immunology

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

14. Defence mechanisms against infections Ready to fight many pathogens Day of Immunology (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 each new pathogen (and can remember afterwards!)

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

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

17. 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! Day of Immunology

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

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

20. Lock-and-Key Principle Day of Immunology

21. 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!!! Day of Immunology

22. Y Y Y Y BUT - Viruses routinely use small variations to evade immune memory! Small variations in the Virus genes Y Y Y Y Small variations in the virus surface structure Reduced protection by Antibody Day of Immunology

23. Bird cell OR RARELY - Large change to completely escape immunity: Y Y Y Y Day of Immunology Large variations in the Virus genes occur in another species Completely different virus surface structures NO protection by Antibody - Bird flu pandemic!

24. 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 Day of Immunology Defence mechanisms against infections (I) Innate Immunity Barriers Blood proteins Phagocytes (II) Acquired immunity Activation of specific immune cells: B- and T-Cells

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

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

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

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

29. ? Day of Immunology 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

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

31. ? Day of Immunology Your Questions?