Why do we have an immune system?

1. Why do we have an immune system?

2. Immune system diseases Non specific immunity Disease survival mechanisms Physical & chemical barriers Infectious Disease Inflammatory Response Transmission Epidemiology Non-specific Cellular response Specific immunity Public Health Vaccination phagocytes NK cells Immunological surveillance Clonal Selection theory T cells B cells Big picture

3. Cells of the Immune System – many cells we will look specifically at these ….. Bone graft Macrophage Mast cell Eosinophil Erythrocytes Marrow Basophil Monocyte Megakaryocyte Bone Hematopoieticstem cell Multipotential stem cell Myeloid progenitor cell Neutrophil Platelets Lymphoid progenitor cell Dendritic cell T lymphocyte B lymphocyte Natural killer cell

4. The human body has the capacity to protect itself against pathogens, some toxins and cancer cells through the immune system GLOSSARY TERMS; • PATHOGEN – DISEASE CAUSING ORGANISMS • TOXINS – POISONS PRODUCED BY ORGANISMS • IMMUNITY – BODY’S ABILITY TO RESIST INFECTION BY A PATHOGEN OR DESTROY THE ORGANISM IF IT SUCCEEDS

5. Learning outcomes • Distinguish between the non-specific and specific immune system • Identify the three lines of defence • Explain the non-specific defences

6. Immune system organisation SPLIT INTO 2 AREAS – NON SPECIFIC AND SPECIFIC • NON-SPECIFIC IMMUNITY WORKS AGAINST ANY TYPE OF DISEASE-CAUSING AGENT • SPECIFIC IMMUNITY WORKS AGAINST A PARTICULAR PATHOGEN

7. Non-specific physical barriers EPITHIAL cells • The first line of defence against infection. • Line the surfaces and cavities of the entire body. • Form sheets/ layers of closely packed cells. SECRETIONS • Some Epithelial cells produce secretions such as enzymes, hormones and lubricating fluids that can defend against infection. • Mucus traps dirt and germs, preventing them from entering the blood. • Various glands produce antimicrobial secretions that help kill microbes.

8. Other physical defences • TINY HAIRS AT THE ENTRANCE TO THE NOSE. • COUGH AND SNEEZE REFLEXES. • ‘FRIENDLY’ BACTERIA.

9. Non-specific immunity • First line of defence are physical and chemical barriers Remember lysozyme - ZZZZZ for sleep in your eye!

10. Immune system organisation • Second line of defence is the Inflammatory response • This occurs if the first line are breached, by a cut/ piercing or an invasion of an infectious organisms

11. Immune system organisation • Second line of defence is the Inflammatory response • This occurs if the first line are breached, by a cut/ piercing or an invasion of an infectious organisms

13. Mast cells histamine vasodilation and increased capillary permeability  secrete cytokines  phagocytosis  complement / antimicrobial proteins  clotting and tissue repair

15. phagocytosis A phagocyte is motile (moves towards pathogen when chemicals detected or antigens). It then engulfs pathogen (endocytosis) – forming a phagocytic vesicle (vacuole) which merges with a lysosome. Lysosomes contain digestive enzymes, which disposes of the pathogen and released by exocytosis. The phagocyte releases more cytokines – positive feedback

16. 2 1. Protein from NK cell inserts a pore into the target cell membrane Natural killer cells 1 Outer membrane on target cell 3 3 protease 3. Signal relayed and genes switched on 2. Signal molecule from NK enters cell 4 vital cell protein 4. “suicide” proteins made 5. “suicide” protein function to make degradative enzymes (protease / DNAase). Destroying vital proteins/DNA 4 Useless fragments of DNA 5 DNAase 5 Useless fragments of protein DNA

17. Natural killer (NK) cells FINAL NON-SPECIFIC DEFENCE • FOR VIRUS AND TUMOUR CELLS PREDOMINANTLY • DISTINCT CLASS OF LYMPHOCYTES WHICH CAN WORK WITH ANTIBODY-DEPENDENT CELLULAR CYTOTOXITY HOWEVER THEY ARE NOT SPECIFIC – WILL ATTACK CELLS (DECIDE SELF/FOREIGN BY LACK OF SELF ANTIGEN (MHC). • A PORE RELEASED FROM NATURAL KILLER (NK) CELL • NK CELL THEN RELEASES SIGNALLING MOLECULES • THIS SIGNALS GENETIC CONTROL OF BOTH SELF DESTRUCTIVE ENZYMES BEING RELEASED AND DNA / VITAL PROTEIN BREAKDOWN • PROCESS OF “CELL SUICIDE”, PROGRAMMED CELL DEATH IS CALLED APOPTOSIS

18. NK CELLS Secondary affect which links to the specific immune system is both NK cells and phagocytes secrete cytokines (interleukins ) that serve to stimulate the specific immune response through the activation of T cells

19. 2 1. Protein from NK cell inserts a pore into the target cell membrane Natural killer cells 1 Outer membrane on target cell 3 3 protease 3. Signal relayed and genes switched on 2. Signal molecule from NK enters cell 4 vital cell protein 4. “suicide” proteins made 5. “suicide” protein function to make degradative enzymes (protease / DNAase). Destroying vital proteins/DNA 4 Useless fragments of DNA 5 DNAase 5 Useless fragments of protein DNA

20. Complement system • THE PRESENCE OF BACTERIA AT THE SITE OF INFECTION STIMULATES ANTIMICROBIAL PROTEINS KNOWN AS ‘COMPLEMENT’ TO ARRIVE AT THE SITE OF INFECTION. • THE COMPLEMENT SYSTEM HELPS THE BODY TO RID ITSELF OF INFECTION BY AMPLIFYING THE IMMUNE RESPONSE.

21. Cytokines .... • Made by damaged tissue / white blood cells • Enhance migration of phagocytes (chemotaxins - chemoattractants) which engulf/digest pathogen and release more cytokines • Deliver antimicrobial proteins faster which amplifies immune response • Deliver blood clotting chemicals (complement) which seals the wound and helps tissue repair • Have a dual purpose; not only in the non-specific defence but also specific defence system by triggering lymphocytes (next lesson)

22. Clotting system • The final stage of inflammation is tissue repair. • What do you remember from unit 2? • What molecules involved? • What is prothrombin / fibrinogen?

23. Non-specific immunity • second line of defence are inflammation cascade and cellular responses

24. Summary slide Non-specific defences Physical defences • Epithelial cells on the body surface and cavity linings form a physical barrier (skin/trachea/oesophagus etc.) chemical defences • Mucus membranes secrete sticky mucus trapping microorganisms • Acid from epithelial cells in stomach destroy ingested microorganisms • Skin sebaceous/sweat glands produce low pH secretions that are too low for most microbes to survive

25. Summary slide Non-specific defences Inflammatory response • Release of histamine by mast cells causes vasodilation and increased capillary permeability. • The increased blood flow and the secretion of cytokines results in the accumulation of phagocytes and the delivery of antimicrobial proteins and clotting elements to the site of infection.

26. Summary slide Non-specific defences Cellular mechanisms • A variety of specialised white blood cells provide protection against pathogens. • Phagocytes recognise surface antigen molecules on pathogens and destroy them by phagocytosis. • Natural killer (NK) cells induce the pathogen to produce self destructive enzymes in apoptosis. • Both Phagocytes and NK cells release cytokines which stimulate the specific immune response. • Complement system amplifies this immune response.