1. Your Body’s Defenses Fighting off Pathogens

2. Infectious Disease Caused by a pathogen (bacteria, virus, fungus, microscopic parasites…) Caused by a pathogen (bacteria, virus, fungus, microscopic parasites…) Transmitted from one individual to another Transmitted from one individual to another Air currents, physical contact, contaminated food or water, animal bite, etc. Air currents, physical contact, contaminated food or water, animal bite, etc.

3. Your Immune System: The “Basics”

4. Nonspecific Defenses What does “nonspecific” refer to? What does “nonspecific” refer to? These defenses provide general protection against any and all pathogens. These defenses provide general protection against any and all pathogens. The defense is not tailored or targeted to a specific antigen (pathogen). The defense is not tailored or targeted to a specific antigen (pathogen). Examples: Examples: Skin and skin secretions Skin and skin secretions Mucous Mucous Fever Fever These either destroy or inhibit the growth/reproduction of pathogens. These either destroy or inhibit the growth/reproduction of pathogens.

5. Specific Defense: Immune System The immune system has many components. The immune system has many components. The white blood cells necessary to mount a targeted attack first form in the bone marrow. The white blood cells necessary to mount a targeted attack first form in the bone marrow. They then differentiate and take on various jobs. They then differentiate and take on various jobs.

6. The body is exposed to countless antigens; each is unique

7. Bacteria

8. Each pathogen has an antigen Antigen: any substance that initiates an immune response. Antigen: any substance that initiates an immune response. May be: May be: Proteins Proteins Lipids Lipids Carbohydrates Carbohydrates Typically, antigens are molecules at the surface of the pathogen Typically, antigens are molecules at the surface of the pathogen

9. Macrophages These cells ingest (“gobble”) pathogens. These cells ingest (“gobble”) pathogens. This helps rid the body of some pathogens. (nonspecific). This helps rid the body of some pathogens. (nonspecific). More importantly, when a macrophage ingests a pathogen it displays pieces of the pathogen at its surface. (specific) More importantly, when a macrophage ingests a pathogen it displays pieces of the pathogen at its surface. (specific) Otherwise known as an “Antigen Presenting Cell”. Otherwise known as an “Antigen Presenting Cell”.

11. Macrophages call to action the Helper T cells Helper T cells coordinate the 2 major activities of the immune response. Helper T cells coordinate the 2 major activities of the immune response. Cell mediated immunity: cytotoxic (“killer”) T cells destroy infected body cells. Cell mediated immunity: cytotoxic (“killer”) T cells destroy infected body cells. Humoral immunity: plasma cells (activated B cells) release antibodies. Humoral immunity: plasma cells (activated B cells) release antibodies. The helper T cell is activated by “lock and key” interaction with a macrophage. The helper T cell is activated by “lock and key” interaction with a macrophage. It then releases chemical signals (cytokines/interleukins) inducing the correct T and B cells to multiply. It then releases chemical signals (cytokines/interleukins) inducing the correct T and B cells to multiply.

13. The attack is now targeted to a specific antigen (Find the enemy! Destroy it!) Antigen

14. Helper T Cells call in the “Killers” Helper T cells activate cytotoxic T cells that have receptors matching the shape of the antigen. Helper T cells activate cytotoxic T cells that have receptors matching the shape of the antigen. These “killer” T cells then find and destroy cells that have been infected. These “killer” T cells then find and destroy cells that have been infected.

15. Helper T cells also bring B cells into the fight By chemical signaling and “lock and key” recognition, the helper T cells activate B cells. By chemical signaling and “lock and key” recognition, the helper T cells activate B cells. B cells then produce millions of antibodies, each with the same shape-the shape that is complementary to the antigen. B cells then produce millions of antibodies, each with the same shape-the shape that is complementary to the antigen.

16. When activated, B cells with the correct receptor divide by mitosis, producing many identical B cells. Some produce antibodies immediately and fight off the initial infection. Others are memory cells that mount an attack against a 2 nd infection.

17. Antibodies Produced and secreted into the blood by B cells. Produced and secreted into the blood by B cells. The antibodies are Y-shaped proteins; each has a specific shape that binds to an antigen. The antibodies are Y-shaped proteins; each has a specific shape that binds to an antigen. The antibodies latch onto antigens causing pathogens to clump together. The antibodies latch onto antigens causing pathogens to clump together. Makes for easier destruction and “clean-up” Makes for easier destruction and “clean-up”

19. Immunity After initial exposure to a specific antigen (primary response), a person is “immune”. After initial exposure to a specific antigen (primary response), a person is “immune”. The pathogen may invade the body again, but does not cause illness. The pathogen may invade the body again, but does not cause illness. The secondary response is fast and effective (due to memory cells), resulting in no symptoms. The secondary response is fast and effective (due to memory cells), resulting in no symptoms. Immunity can be acquired by: 1)Fighting off an illness caused by the pathogen. 2)Vaccination: causes a primary response to the antigen, without causing illness.

20. Primary vs. Secondary Response

21. Vaccination (a.k.a. Immunization) Vaccine: contains inactivated bacterial toxins, or weakened microbes, etc. that will stimulate an immune response, because they are seen as antigens. Vaccine: contains inactivated bacterial toxins, or weakened microbes, etc. that will stimulate an immune response, because they are seen as antigens. Because the modified pathogens are harmless, vaccines don’t result in illness. Because the modified pathogens are harmless, vaccines don’t result in illness. The memory cells produced during the primary response will protect you against future illness caused by the pathogen. The memory cells produced during the primary response will protect you against future illness caused by the pathogen.

22. Common Vaccines Measles Measles Mumps Mumps Polio Polio Chickenpox Chickenpox Rubella Rubella Tetanus Tetanus Hepatitis B Hepatitis B Influenza (many types) Influenza (many types) Diphtheria Diphtheria

23. Short-term Immunity Passive immunity: Passive immunity: A pregnant woman passes antibodies to her child through the placenta. A nursing mother passes antibodies to the child through breast milk. A pregnant woman passes antibodies to her child through the placenta. A nursing mother passes antibodies to the child through breast milk. An injection of antibodies from an immune animal or human is given to a person. Example: a person bit by an animal with rabies is injected with antibodies. An injection of antibodies from an immune animal or human is given to a person. Example: a person bit by an animal with rabies is injected with antibodies.