The Body’s Defense System How does the body identify and destroy pathogens?

What is a pathogen? a microorganism such as a virus, bacterium, prion, or fungus, that causes disease in a plant or animal

Prions Infectious Protein No DNA or RNA NOT LIVING AKA spongiform (like a sponge) encephalopathies (pathogen of the brain) Mad Cow Disease - Cows Scrapie - sheep Kuru – humans New Guinea,

Virus Has two components Protein covering Nucleic acid (either RNA OR DNA, rarely both) inside Infect and “take over” the cell’s replication machinery Colds, Influenza, HIV

Virus

Cold and HIV Virus

Streptococcus Bacteria Living prokaryote!

Non-specific vs. Specific Immune Response Barriers Separate the organism from its environment Nonspecific immune response – second l Inflammatory Response Repel and destroy foreign “cells” Specific immunity How lymphocytes identify and remember certain types of invasive bacteria, viruses, toxins. Create a “rapid defense system” for any second attack

First Line of Defense - Barriers Skin Mucous membranes Secrete mucus (all “openings” to the environment) Mucus contains lysozyme (kills bacteria) Others Cilia (Resp. system) Stomach acid (low pH kills bacteria) Enzymes (lysozyme in tears) Respiratory tract

Second Line: Non Specific Immunity Inflammatory Response Histamine triggers the response Increases the permeability of capillary membranes (lets white blood cells out of the capillaries) Phagocytes/macrophages – ingest invaders Natural Killer cells – lymphocytes that provide a rapid response to a viral infection. Help contain a viral infection while antibodies are being made.

Inflammatory Response Increased blood flow RESULT: Redness, swelling, pain, warmth, Clotting (if blood vessel damaged)

Match these to the conditions (next page)

Effects of inflammation Pain Heat Swelling Redness Loss of function (sometimes) Chronic (long term) inflammation (depending on location  Periodontitis (gums) Atherosclerosis (blood vessels) Crohn’s disease (intestines) Hayfever (respiratory system) Arthritis(joints)

Fever Increase body metabolism , speeding up the repair process (only up to 104 F) Slow down the reproduction of some bacteria and viruses . Makes YOU slow down and “rest”

How does fever help? (1) Fever slow down some bacteria and viruses. (2) Fever increase metabolism (enzymes work faster up to 104 F) (3) fever makes a patient feel ill, condition which makes the patient more likely to rest.

Protein Production Complement proteins Interferon Stimulate inflammation and phagocytosis Interferon Send warning signals to neighboring cells Released by a cell which was attacked by a virus

How does the body know to “stop” the inflammatory response Programmed cell death (apoptosis) Based on lack of presence of pathogen (foreign antigens) Signal sent to “self destruct”.

What if the bacteria is too strong?

Specific Immunity Cells and Tissues that learn about and learn to recognize and attack foreign substances (based on antigen recognition) Include Macrophages(from general response) T-cells B cells

Role of each Cell Cell mediated immune response Macrophages/phagocytes – engulf (eat) foreign invaders T cells - identify and destroy infected cells; communicate with B cells Humoral Immune response B cells – produce antibodies, immune memory Antibodies – specific proteins design to restrict spread of pathogen

Chemicals “call” cells When macrophage “eats” the bacteria it “displays” antigens Helper T binds to antigens Result: chemical message released more Helper T made Killer T activated Communicate with B cells

Chemical signals 

B cells create Antibodies Bind to a surface antigen on bacteria and clumps them together so that macrophage can “eat them” Complement proteins Put holes in bacterial cells Can inactivate or destroy toxins

Antibodies and complements Antibodies bind to antigens

Once all is under control Chemical messages decrease B and T cells IMMUNE MEMORY Memory B cells are formed Future rapid response cells Circulate in blood

Memory T Cell Suppressor T Cell Memory B Cell

Memory Cells The next time that an individual encounters that same antigen, the immune system is ready to destroy it quickly.

What prevents Reinfection? MEMORY CELLS Long term protection against re-infection for life How? Memory B cells remain in the blood. (Bone marrow can remake as needed) Recognize antigen (second time response) Rapid and large production of specific antibodies

Ways to obtain immunity Short –term immunity Some vaccines or fluids containing antibodies Infants have antibodies from mother Due to blood exchange during pregnancy Due to mother nursing child Long-term immunity Stimulated by infection Can be obtained through vaccines made from infectious agents that are not infectious, but do cause antibodies to form

Short term vs. Long term Immunity Body has been exposed to infective agent Disease or vaccine Short term immunity Individual given antibodies (but the body has not learned how to make more)

Vaccines vs Antibiotics vs. Antivirals Create a table with three columns and four rows In the first column Vaccine Antibiotic Antiviral

Vaccines, Antibiotics, Antivirals Column 1 – When are they used (before or during or after infection?) Column 2 – What are they effective against? Column 3 - Do they treat, prevent, or cure? Column 4 Do you have other questions or comments to add?

Virus consumed by a macrophage 2. Macrophage displays the virus antigens 3. Helper T-Cell recognizes “enemy” . Call in the troops. 4. B cells and Killer T Cells are manufactured 5. B cells produce antibodies that bind the virus. Killer T Cells destroy infected body cells. 6. Suppressor T cells stop production of defense. 7. Memory cells remain for future rapid response.