The Immune System

The Nature of Disease Infectious Diseases: Diseases, such as colds, that are caused by pathogens that have invaded the body. Pathogens include: –Bacteria – viruses –fungi –protists

Koch’s Postulate

The Spread of Disease a. Air b. Food c. Water d. Person-to-person contact e. Bites by animals

Nonspecific Defenses Innate Immunity: Defenses that help protect the body against any pathogen, regardless of its identity.

First-line of Defense Barriers: A.Skin- physical barrier to pathogens. B.Mucus Membrane- epithelial tissue that protect the interior surfaces of the body.

Skin The skin blocks pathogens from entering the body. It also releases sweat, oils and waxes that contain chemicals that are toxic to pathogens. –ex. sweat contains lysozyme an enzyme

Mucus Membrane The mucus membrane serves as a barrier and secretes mucus. This is a sticky fluid that traps pathogens. Lines the respiratory and digestive systems and the urethra.

Second-line of Defense When a pathogen gets past the first line of defense A. Inflammatory Response- a protective response of tissue affected by disease or injury, characterized by redness, swelling and pain. –Histamine- is released by damaged cells and increases blood flow to the area –Histamines attract white blood cells to the affected area

Second line of Defense Cells involved in the inflammatory response: Phagocytes- Ingest and destroy pathogens –Neutrophil- Ingest pathogens they encounter –Macrophage- engulfs pathogens and cellular debris. White blood cells that attack pathogen-infected cells. ex. cancer and viruses

Second line of Defense B. Temperature Response – a moderate fever may slow bacterial and viral growth and promote white blood cell activity. C. Proteins – Complement proteins circulate in the blood and become active when they encounter certain pathogens. –puncture membrane of infected cells –Interferon- released by virus-infected cells to help nearby cells resist infection

Specific Defense The Immune System: The cells and tissue that recognize and attack foreign substances in the body.

Components of Immune System A. Lymphocytes – The white blood cells - B cells and T cells B. Thymus - gland above the heart that helps produce a special kind of lymphocyte (T- cells) C. Spleen – Stores healthy blood cells and helps develop lymphocytes and other white blood cells

Recognizing Pathogens Lymphocytes can recognize foreign invaders by their antigens. Antigens are any substance that the immune system can recognize and react with. Lymphocytes have unique receptor proteins bind to antigens and start a specific attack called an immune response.

Immune Response 1. Pathogen enters your body a.Contains an antigen 2. Macrophages engulf (eat) these pathogens 3. Macrophages present the antigen on its surface 4. Helper T- cell recognizes this antigen with a receptor and is activated

Immune Response 5. Helper T cell activates B cell and it divides 6. B cells become plasma cells 7. Plasma cells secrete antibodies 8. Antibodies bind to antigen and mark them for destruction

Antibodies Antibodies – a protein that reacts to a specific antigen or that inactivates or destroys toxins

Innate vs. Acquired Immunity Innate Immunity: Skin barriers and body secretions –Not specific Acquired Immunity: Specific response to a specific antigen

Immunity and Vaccination Immunity – the ability to resist an infection disease Vaccination – the introduction of antigens into the body to cause immunity.

Vaccine Vaccine - a solution that contains dead or weakened pathogens. Since the antigens are still present the body produces an immune response. Can be oral (live and weakened) or injected (heat-killed toxoid). ex. Polio, measles, mumps, tetanus, small pox

Problems of the Immune System When the immune system reacts to harmless antigens in ways that can be harmful. Allergies – physical response to an antigen. ex. pollen, animal dander and food. Asthma – a respiratory disorder that causes the bronchioles to narrow because of an overreaction to a substance in the air.

Problems Autoimmune Disease – when the immune system attacks the organism’s own cells ex. Multiple sclerosis Rheumatoid arthritis Thyroiditis

Improper Functions AIDS (acquired immunodeficiency syndrome) –Causes the immune system to lose its ability to fight off pathogens and cancers. Caused by the virus HIV that attacks the T cells. –T-cells are not able to activate proper immune responses

Bacteria vs. Viruses Bacteria Viruses

- Living- Non-living -Prokaryotes- parasite -treat with antibiotics - can not reproduce on its own - can not obtain its own energy Bacteria vs. Viruses

Bacteria Viruses Replication:Non-living, require a Binary Fissionhost to replicate Immune Response:Antibodies, macrophages Treatment:Some antivirals, but normally Antiobiotics No treatment

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