Chapter 19.2 Pages 442-448 Transmission
Immunity There are three lines of defense: 1 The skin and mucous membranes are a nonspecific barrier to infection. 2 Macrophages attack pathogens that enter the body and cause an immune response. 3 Lymphocytes initiate a specific response by targeting specific pathogens and try to contain them.
First Line of Defense: Skin and Mucous Membranes The skin and mucous membranes secretion are nonspecific defenses. skin Protects against organisms living on the body surface. Sheds and takes pathogens with it. has a low ph that helps to repel microorganisms. glands Secretes chemicals that slows the growth of bacteria. Examples: tears and saliva: has enzymes that break down bacteria earwax: traps microorganisms digestive secretions (acids): kill microorganisms that enter the stomach Mucous membranes on the surface of respiratory, digestive, urinary, and reproductive tracts: secrete mucus that traps pathogens, which are coughed or sneezed away from the body, destroyed in the stomach, or excreted in the urine or feces. Vomiting Removes toxins or infectious agents.
Second Line of Defense White blood cells: Phagocytes and Macrophages Natural Killer Cells Inflammation Defensive proteins Interferons Complement Proteins Fever
White Blood Cells (WBC) Phagocytes are white blood cells that attack and eat foreign cells. Macrophages are phagocytic white blood cells. They move through the lymphatic fluid, cleaning up dead and damaged cells. To destroy cells, macrophages extend their long pseudopodia, grab the foreign organism, and eat it. Pseudopodia are cell extensions used for eating and moving. Enzymes inside the macrophage help break the foreign organism apart. Macrophages clean up old blood cells, dead tissue, and other cell debris. Macrophages release chemicals that stimulate the production of more white blood cells. Most foreign cells are destroyed in lymph nodes.
If a foreign organism is too big for phagocytosis, other white blood cells surround the foreign organism and secrete digestive enzymes that irritate or even destroy the organism. This happens with protozoans and worms. WBCs
WBCs: Natural Killer Cells Natural killer cells are nonspecific cells that attack tumor cells and virus - invaded body cells on first exposure. These cells release chemicals that break apart plasma membranes of their target cells, causing them to burst.
At Infection Site When white blood cells are actively fighting an infection, the body increases production of white blood cells, and white cell counts increase alot. At the site of infection, tissue fluid, dead cells, and microorganisms make pus. If the pus cannot drain, an abscess will form.
Inflammation When there is tissue injury, the inflammatory response begins. Damaged cells release histamine. Histamine causes vasodilation near the injury. More blood and cells arrive at the site of infection to help repair and cause redness, warmth, and swelling to happen. More blood brings oxygen and nutrients needed for healing tissue.
Defensive Proteins: Interferons Some proteins act as nonspecific defenders. These are defensive proteins. Interferons are proteins produced by virus-infected body cells to help uninfected cells resist infection. When infected cells die, they release interferon that bind to receptors on uninfected cells and stimulate the healthy cells to produce proteins that inhibit viral production.
Defensive Proteins: Complement Proteins There are 20 different complement proteins in the blood that help other defense mechanisms. Complement Proteins: Coat the surfaces of microbes, so macrophages can eat them. Can put holes in the membrane surrounding microbes, causing them to break apart. Increase the inflammatory response.
Fever Body temperature above 97-99⁰F is a fever. Macrophages release pyrogens. Pyrogens cause body temperature to increase. A slightly higher than normal temperature decreases growth of bacteria and increases the metabolic rate of healthy body cells. This helps fight infection by slowing pathogen reproduction and allowing tissue repair. When infection is controlled, macrophages stop releasing pyrogens, and body temperature returns to normal.
Third Line of Defense: Lymphocytes Cells of the immune system identify and attack specific microorganisms that are recognized as foreign. This specific defense system consist of millions of white blood cells, called lymphocytes. Lymphocytes travel through the blood and lymphatic system.
Antigen Antigens are molecules that are foreign to the host and stimulates the immune system. Examples of antigens are molecules found on viruses, bacteria, fungi, protozoans, worms, dust, pollen, or transplanted tissues.
B cells and T cells When an antigen is in the body, two types of lymphocytes can be produced: the B lymphocytes (B cells) and T lymphocytes (T cells). Lymphocytes are specific because their antigen receptors recognize specific antigens.
B cells versus T cells B cells B cells recognize and react to small, free living micro organisms such as bacteria and the toxins they make. B cells secrete proteins (antibodies) that bind to and inactivate antigens. T cells T cells recognize and respond to body cells that have errors, such as cancer cells or cells invaded by viruses, transplanted tissues, and larger organisms such as fungi and parasitic worms. T cells do not produce antibodies but directly attack foreign cells.
Passive Immunity vs Active Immunity Antibodies are found in lymph, intestines, and tissue fluids. They are also found in breast milk. When a baby breastfeeds, some antibodies are passed from the mother to the baby. This is short term passive immunity for the child. The immunity will last as long as the antibody lasts in their blood. When a child is exposed to an antigen, antibodies are produced. This is called active immunity.
Questions 7 1. The first line of defense is and. 2. The second line of defense are,,, and. 3. The third line of defense is. 4.,, and are white blood cells. 5. of macrophages are cell extensions used for eating and moving. 6. are nonspecific cells that attack tumor cells and virus-invaded body cells on first exposure. 7. are proteins produced by virus-infected body cells to help uninfected cells resist infection. 8. There are 20 different in the blood that help other defense mechanisms. 9. cause body temperature to increase. 10. are molecules that are foreign to the host and stimulates the immune system. 11. secrete proteins (antibodies) that bind to and inactivate antigens. 12. do not produce antibodies but directly attack foreign cells. 13. occurs when a baby breastfeeds. 14. occurs when a child is exposed to an antigen.
An allergy is an immune response that happens when there is no pathogen. The body reacts to the non harmful substance like it is a pathogen. Example: some people have allergies to peanuts or ragweed pollen. Allergy
Anticipating Infection The ability to respond to an infection is the immune response. Lymphocytes develop from stem cells in the bone marrow and then move into the blood stream. Lymphocytes that continue their development in the bone become B cells. Lymphocytes that move to the thymus to continue their development become T cells.
Antigen Diversity Genetic rearrangements allows for millions of different antigen receptors to be made. As a result, we can respond to a million different antigens.
Self vs Nonself Developing lymphocytes are tested in the thymus to determine whether they are self or non self. Lymphocytes that bind to antigens on testing cells are destroyed; those that do not bind are allowed to develop.
Autoimmune Disease When self vs non self testing fails, the cells of the immune system attack normal body cells. This disease is an autoimmune disease. Examples of autoimmune diseases: Multiple sclerosis occurs when T cells specific for protein on nerve cells attack these cells in the brain. In insulin-dependent diabetes, T & B cells attack cells that produce the hormone insulin in the pancreas.
Cell Mediated Immunity
Antibody-Mediated Immunity B cell protection is humoral immunity. B cells do not directly kill cells with antigens. B cells make and secrete antibodies that help the body remove antigenic cells. When a B cell binds an antigen, the B cell makes copies of itself. This copy is a memory cell carrying the same antibody. This clonal population is a population of identical cells. Now all cells of the clonal population can help in overcoming infection. After infection, some memory cells remain and are able to recognize the antigen in the future.
Questions 8 1. An is an immune response that happens when there is no pathogen. 2. B cells develop in the. 3. T cells develop in the. 4. The self vs non-self test occurs in the. 5. An disease occurs when self vs non self testing fails causing the cells of the immune system to attack normal body cells. 6. occurs when T cells specific for protein on nerve cells attack these cells in the brain. 7. attack and kill body cells that have been infected with a pathogen. 8. secrete a substance that enhances cell-mediated immunity and antibody-mediated immunity.