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Immune System INTRODUCTION TO IMMUNITY What is immunity? The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells What is an immune system? The system in the body responsible for maintaining homeostasis by recognizing harmful from non harmful organisms and produces an appropriate response Types of immunities Natural Active Immunity: Body is exposed to infection and naturally produces antibodies to fight off specific infection Natural Passive Immunity: occurs when the mother transfers immunity to her unborn fetus through the placenta or to a newborn through breast milk Types of Immunities Continued Artificial Active Immunity: results from the administration of a vaccine which induces the formation of antibodies for that specific infection. Artificial Passive Immunity: occurs as a result of taking premade antibodies that provide temporary protection for people who have been exposed to a specific illness. White Blood Cells: Brains behind the Immune Operation 1. Granulocytes (50-60%) (basophil, eosinophil, neutrophil) release powerful granules that have chemicals inside that attack an intruder *Basophil produce histamine *Eosinophil (capture invading bacteria *Neutrophil (aid in phagocytosis) 2. Monocytes (7 %) When activated become macrophages that engulf antigens 3. Lymphocytes (30-40 %) T- Cells and B-Cells ***All WBC are produced in the bone marrow as stem cells – T-cells migrate to the thymus – that’s where they mature ***WBC are found in lymph nodes, spleen & liver How does the body fight infection/foreign invaders? The Body’s THREE lines of Defense First Line of Defense – The Skin • Provides Physical and Chemical barriers Physical – hard to penetrate, made of indigestible keratin Chemical – tears, sweat, saliva and mucous (chemicals and enzymes in body fluids) First Lines of Defence saliva antibacterial enzymes skin prevents entry stomach acid low pH kills harmful microbes tears antibacterial enzymes mucus linings traps dirt and microbes “good” gut bacteria Second Line of Defense – Nonspecific Immune Response These are defenses the body uses no matter what the invader may be. These defenses include: Phagocytosis – done by Macrophages Inflammation - caused by release of Histamine from leukocytes Fever – caused by histamines. The fever (high temp) kills invaders by denaturing their proteins. Phagocytosis Stages in phagocytosis 1. Phagocyte detects chemicals released by a foreign intruder (e.g. bacteria) 2. Phagocyte moves up the concentration gradient towards the intruder 3. The phagocyte adheres to the foreign cell and engulfs it in a vacuole by an infolding of the cell membrane. 4. Lysosomes (organelles which are rich in digestive enzymes & found in the phagocytes cytoplasm) fuse with the vacuole & release their contents into it. Phagocytosis 5. The bacterium is digested by the enzymes, and the breakdown products are absorbed by the phagocyte. During infection, hundreds of phagocytes are needed. Injury Chemical signals are released by the foreign invader Chemicals cause capillaries to dilate thus increasing blood flow Basophils flow through the blood stream and gather to the site of infection and release histamine (histamine cause inflammation and increase blood flow) This brings neutrophils and monocytes to the site Neutrophils release chemicals that engulf and kill antigens * they have a short lifespan but are constantly supplied * dead neutrophils form pus macrophages engulf and kill antigens and dead neutrophils ***Inflammation response (swelling, heat, redness & pain) Third Line of Defense – Specific Immune Response ***This is a specific response to a specific pathogen/antigen. The response involves lymphocytes and the creation of Antibodies. There are 2 types of lymphocytes : ***T-cells – identify and attack foreign substances, regulate B-cell production and stop the immune response ***B-cells – produce antibodies and are programmed to respond to a specific antigen Antigens all cells have surface markers called antigens. body can recognize these as self or nonself (foreign) Specific response Lymphocytes detect presence of foreign antigens Stimulated to produce specific proteins called antibodies. How an antibody operates/works? Deactivation of a bacterium by an antibody. The Pathway of Specific Immune Response Step 1 Pathogens eaten by Macrophage Step 2 Displays portion of Pathogen on surface Step 3 Pathogens Helper-T cell recognizes Pathogen Activates B- Cell Activates Cytotoxic T- Cell Memory T-Cell Memory B-Cell Antibodies Kills Infected Cells Immune Response Explained 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Antigen infects cells. Macrophage ingests antigen and displays portion on its surface. Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active. Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells. Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells. Active Cytotoxic T-Cells kill infected cells. At the same time, B-Cells divide into Plasma Cells and Memory BCells. Plasma cells produce antibodies that deactivate pathogen. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears. Supressor T-Cells stop the immune response when all antigens have been destroyed. Cellular Immunity .vs. Antibody Immunity Cellular Immunity Antibody or Humoral Immunity Carried out by T-Cells Carried out by B-cells Infected cells are killed by Antibodies are produced and Cytotoxic T –Cells. dumped into blood stream. Antibodies bind to antigens and deactivate them. Immune Response Summary Displays copy of antigen on surface of cell Antigen Macrophage Helper T - Cell Cellular Immunity Active Cytotoxic T-Cell Kills Infected Cells Memory T- Cell Antibody Immunity Active B - Cell Plasma Cell Antibodies Deactivates Antigens Memory B-Cell What happens during an allergic reaction? Anaphylaxis or anaphylactic shock: This is the sudden and severe allergic reaction to a substance that can cause death. During an allergic reaction antibodies cause histamines to be released from certain cells. In addition blood vessels dilate which causes a decrease in blood pressure and heart rate. Histamines cause: a. Swelling of tissues b. Release of fluids (runny noses and eyes) c. muscle spasms (some cases) Treatments for Allergies 1. Avoidance of material – especially food. 2. Epinephrine – “epi – pen” 3. Antihistamines -- benadryl