Human Immunity Ch. 40

I.Infectious Disease A. Disease 1. Any change (other than injury) that disrupts normal body function 2. Caused by pathogens B. Pathogens 1. Disease causing agent such as bacteria, virus, protist, worm or fungi

C. Germ Theory of Disease 1. For thousands of years, humans believed sickness was caused by curses, evil spirits or angry gods 2. “Germ Theory of Disease”- Louis Pasteur and Robert Koch observed that infectious diseases are caused by microorganisms

150 km/hr sneeze!

D. How Diseases are Spread 1. Physical contact a. Direct – touching an infected person b. Indirect – through the air or on objects 2. Contaminated Food or Water a. Be sure to cook food thoroughly and sanitize water 3. Infected Animals a. Vectors – animals that transmit disease to humans Ex: malaria from mosquito or bubonic plague from fleas

E. Fighting Infectious Diseases 1. Wash your hands frequently 2. Drugs specific to pathogen (ex: penicillin) 3. Rest, plenty of fluids, good nutrition 4. Your immune system! White Blood Cell

II.Immune System A. What is immunity? 1. The ability of the body to resist pathogens 2. Function of immune system is to fight infection through the production of cells that inactivate foreign substances B. Human immune system includes two general categories against infection: 1. Non-specific defenses 2. Specific defenses

III. Nonspecific Immunity A. First Line of Defense 1. Skin – how? 2. Mucus membranes, saliva and tears have antimicrobial proteins ( lysozymes ) that break down the cell wall of bacteria 3. Oil and sweat glands create an acidic environment that slows the growth of bacteria 4. Digestive and respiratory systems - how? B. Second Line of Defense (once infected) 1. Inflammation - how? 2. Fever - how? 3. White blood cells (phagocytes) engulf foreign particles 4. Interferons - proteins that interfere with viral replication

Skin Wound Bacteria enter the wound Phagocytes move into the area and engulf the bacteria and cell debris Capillary The Inflammatory Response (DRAW FIG PG. 1037)

IV. Specific Immunity A.When a pathogen gets past the body’s non- specific defense, a specific Immune response is triggered 1.Targets specific individual invaders 2.You are born with this system 3.You are able to recognize millions of invaders B. Antigen is any substance that triggers an immune response 1.Recognized by two types of lymphocytes (white blood cells) called B cells and T cells 2. B cells provide immunity against antigens and pathogens in body fluid 3. T cells provides defense against abnormal cells and pathogens in living cells

C.Humoral Immunity (body fluids) 1. When B cells recognize a pathogen, large numbers of plasma cells and memory B cells are produced 2. Plasma cells release antibodies to attack the pathogen a. Antibodies = “Y”-shaped proteins that recognize and bind to antigens, helps to destroy specific pathogens 3. Once exposed to a pathogen, millions of memory B cells remain, thus reducing the likelihood of a 2 nd infection DRAW Figure 40-8, pg 1038 Antigen- binding sites Antigen Antibody

Humoral Immunity ( DRAW FIG. 40-9, 1039 )

Humoral Immunity Movie

D. Cell Mediated Immunity 1. Body’s primary defense against cells that are cancerous or infected by viruses. Also important in fighting infection caused by fungi and protists. 2. Begins with a wandering macrophage (WBC) engulfing a foreign particle (the antigen).

3. The antigen is broken down and pieces of the surface proteins of the pathogen are moved to the surface of the macrophage 4. This is done by the HLA protein. It is unique to each person and displays both self and non- self antigen fragments

5. Only T-cells that have receptors that fit to the presented antigens bind to the macrophage. 6. Binding of the T cells with the macrophage stimulates these specific T-cells to divide many times forming many different kinds of T-cells.

7. Helper T cells (activated by binding to macrophage) stimulates the production of memory T cells and killer T cells 8. Memory T cells (like memory B cells) will “remember” the antigen and cause a secondary response if seen again 9. Killer T cells then track down and kill any substance with those antigens (pathogen or body cell) Macrophage T Cell Helper T Cell Killer T Cell Infected Cell Antigens are displayed on surface of macrophage T cell binds to activated macrophage T cell, activated by macrophage, becomes a helper T cell Helper T cell activates killer T cells and B cells DRAW FIG 40-10, pg Killer T cells bind to infected cells, disrupting their cell membranes and destroying them

E. Transplants 1.In transplant patients, T-cells recognize foreign markers on the cell surface of the transplanted organ and try to kill the cells. 2.This is organ rejection

V.Acquired Immunity A. Active Immunity - body makes its own antibodies in response to an antigen 1. Vaccine a. Take a virus or other pathogen and destroy or weaken its nucleic acid. Why do we want to do this? b. You can alter the DNA of the pathogen by using chemicals, radiation or growing it in a different host. Why are you asked if you are allergic to eggs before you get a flu shot? c. Leave the protein coat undamaged.  Why?

d. Inject this mixture (the vaccine) into humans or other animals. e. Your body responds as if you had the disease and you form memory cells for this disease. Why don’t you get this disease? f. Next time host is exposed to the pathogen, the body will recognize and destroy pathogen before the disease affects the body. Why can you fight it off so fast?

B. Passive Immunity - antibodies produced by another animal are used by another organism 1.Mother passes antibodies on to fetus/baby 2.Antibodies are injected into travelers to protect them from tropical diseases such as malaria

VI.Immune System Disorders A.Allergies – overreaction to antigens called allergens (dust, mold, pollen and bee stings, etc) 1.Causes release of histamines a.Increase blood flow and fluids to surrounding area b.Increased mucus production, sneezing and inflammation 2. Anaphylactic shock – severe allergic reaction that involves one of more body systems a.Inflammation of respiratory system b.Drop in blood pressure (starves the brain of O 2 ) c.Can result in death

B.Asthma – chronic respiratory disease 1.Triggered by allergens, stress, exercise, smoke, etc. 2.Narrowing of air passages causes wheezing, coughing and difficulty breathing 3.No cure, but medications can control symptoms C.Autoimmune diseases – immune system mistakenly attacks the body’s own cells 1.Includes Type I diabetes, rheumatoid arthritis, myasthenia gravis, and multiple sclerosis D.AIDS (Acquired Immune Deficiency Syndrome) 1.Caused by the human immunodeficiency virus (HIV) a.Exists in blood and body fluids b.Retrovirus (RNA) that evades the defenses of the immune system and attacks helper T cells c.Leaves the body without protection from pathogens

Cell Beach Movie

2. The lower the T cell count, the more advanced the disease 3. AIDS does not directly kill patient, secondary infection does (pneumonia most common) 4. Transmission of HIV a. Sexual activity (intercourse and oral) b. Sharing needles c. Blood contact d. Infected mother during pregnancy, birth, or breast-feeding

HIV Movie

5. AIDS Treatment a. No cure b. Drugs to suppress the virus (drug “cocktails”, AZT)