Chapter 45 Outline.

I. Nonspecific Defenses

                        1. The immune system is our primary defense against disease-causing                             microorganisms.

                        2. Nonspecific defenses are the body’s first line against disease.

            A. The Skin and Other Barriers

                        1. The body’s most important nonspecific defense is the skin.

                        2. Very few pathogens can penetrate the layers of dead cells at the skin’s outer surface.

                        3. Lysozyme is an enzyme that breaks down the cell walls of many bacteria.

            B. Phagocytes and Inflammation

                        1. The second line of defense is called the inflammatory response.

                        2. Bacteria are attacked by phagocytes, which are white blood cells that engulf and destroy bacteria.

                        3. If the infection remains small and in one place, it is said to be inflamed.

                        4. Sometimes an infection spreads through the lymphatic system to the lymph nodes, where it causes swelling and tenderness of the nodes as the battle between pathogen and white blood cells continues.

                        5. A fever is when the immune system responds by producing more white blood cells, and releasing chemicals that stimulate the action of these white cells by increasing the body’s temperature.

            C. Interferon

                        1. Interferon “interferes” with the virus by inhibiting the synthesis of viral proteins in infected cells and helps block viral replication.

                        2. If a pathogen is able to get past the body’s nonspecific defenses, the immune system reacts with a series of specific defenses that attack the disease-causing agent.

                        3. A substance that triggers the specific defenses of the immune system is known as an antigen.

II. Specific Defenses

            A. The Immune Response

                        1. The key cells of the immune system are lymphocytes, a type of white blood cell.

                        2. B-lymphocytes, which mature in the bone marrow, are responsible for producing antibodies.

                        3. An antibody molecule is shaped like the letter Y and has two identical antigen-binding sites that precisely fit the shape of a particular antigen.

                        4. Agglutination is when viral antigens attach to a group of antibody molecules that can link the viruses together in a large mass.

                        5. Plasma cells are specialized B cells that release antibodies into the bloodstream to deal with the infection.

                        6. The production of antibodies from the first exposure to an antigen is known as the primary immune response.

                        7. The activation process is assisted and regulated by lymphocytes that have matured in the thymus gland and are known as T-lymphocytes.

            B. Immunity

                        1. Immune is when you build up a permanent resistance to a disease.

                        2. Once the body has been exposed to a disease, a large group of B-cells and T-cells remains capable of producing a secondary immune response should the pathogen reappear in the body.

                        3. Vaccination is the injection of a weakened or mild form of a pathogen to produce immunity is known as vaccination.

                        4. The immunity produced by a vaccine is known as active immunity because the body has the ability to mount an active immune response against the pathogen.

                        5. If antibodies produced by other animals against a pathogen are injected into the bloodstream, they produce a passive immunity against the pathogen as long as they remain in the circulation, usually for several weeks.

            C. Cell-Mediated Immunity

                        1. The most effective attacking cells in the immune system are killer T-cells.

                        2. An immune response, which is called cell mediated immunity, is particularly important in the case of diseases caused by eukaryotic pathogens, such as fungi and protozoa.

                        3. Gradually, the immune system damages and destroys the transplanted organ, a process known as rejection.

III. Immune Disorders

                        1. The impressive power of the immune system to defend the body against a wide range of potential pathogens comes at a price.

            A. Allergies

                        1. The most common overreactions of the immune system are known as allergies.

                        2. When allergy-causing antigens attach themselves to mast cells, the activated mast cells release chemicals known as histamines.

                        3. One of the most serious allergic reactions is asthma, a condition in which smooth muscles contract around the passages leading to the lungs, making breathing difficult.

            B. Autoimmune Disease

                        1. When the immune system attacks the body’s own cells it produces an autoimmune disease.

                        2. A condition known as rheumatic fever is when antibodies and killer T- cells cause cell death and scarring of the heart lining and the heart valves.

                        3. Rheumatoid arthritis is a destructive inflammation of the joints.

                        4. Juvenile-onset diabetes may be the result of an autoimmune reaction against the insulin-producing cells of the pancreas.

                        5. Multiple sclerosis is a nerve disease that results from an autoimmune destruction of the myelin sheath that surrounds nerve fibers.

            C. AIDS

                        1. Acquired Immune Deficiency Syndrome, or AIDS, is a dramatic example of what happens when cells of the immune system are weakened by infection.

                        2. The virus that causes AIDS was first discovered in 1984 and was named human immunodeficiency virus, or HIV.

                        3. Once HIV enters the body, it attaches to receptors on the surfaces of a type of T-cell known as helper T-cells.

                        4. You can prevent aids by avoiding exposure to HIV, the virus that causes the disease.