The Immune System

II. How diseases are spread 1.Physical contact 2. Contaminated food and water 3. Infected animals (vectors) III Fighting Infectious Diseases 1. Antibiotics 2. Antiviral Drugs 3. Over –the-- Counter Drugs I. Agents of Disease 1. Viruses (influenza, small pox) 2.Bacteria ( botulism, diphtheria) 3.Protists ( malaria, sleeping sickness, amoebic dysentery) 4. Worms(schistosomiasis) 5.Fungi( ringworm)

Immune system -functions to fight infection through the production of cells that inactivate foreign substances or cells -2 general categories of defense mechanisms: I. Nonspecific Defenses  Do not discriminate between 1 threat and another; include physical and chemical barriers A. First line of Defense 1. Function: to keep pathogens out of the body 2. Carried out by skin, mucus, sweat and tears 3. Body’s most important nonspecific defense is the skin. Lysozyme– an enzyme that breaks down the cell walls of many bacteria.

Second line of Defense 1. Inflammatory response- a second line of defense 2. when pathogens are detected immune system produces millions of white blood cells(WBCs), which fight infection 3. Blood vessels near the wound expand and WBCs move from the vessels to enter the infected tissues. 4. Many of these WBCs are phagocytes, which engulf and destroy bacteria. 5. Infected tissues become swollen and painful. 6. Immune system releases chemicals that increase the core body temperature(FEVER)

Interferons 1. Produced by virus-infected cells 2. Are proteins that help other cells resist viral infections 3. Inhibit the synthesis of viral proteins 4. Help block viral replication 5. Slows down the process of infection and gives the specific defenses of the immune system time to respond.

Specific Defenses(immune response) Antigen- any substance that enters the body to rigger the immune response. Humoral Immunity  Provides immunity against antigens and pathogens in the body fluids  Fighting cells in this response: B lymphocytes( B cells)  B cells sense pathogens, grow and divide rapidly, producing large #s of plasma cells and memory B cells  Plasma cells release antibodies, proteins that recognize and bind to antigens  Antibodies carried in the bloodstream to attack pathogens  Once body is exposed to a pathogens, millions of memory B cells remember how to produce antibodies specific to that pathogen– secondary response (reduce chance that the disease can develop a 2 nd time.)

Cell-Mediated Immunity 1. Defense against its own cells and pathogens inside living cells 2. Fighting cells in this response: T cells 3. The body’s primary defense against it own cells when they have become cancerous or infected by viruses. 4. Also important infection caused by fungi and protists 5. When viruses get inside living cells, antibodies alone unable to destroy them. 6. T cells divide and differentiate into: a. Killer T cells(cytotoxic T cells)/these track down and destroy bacteria, fungi, protozoan or foreign tissue that contains the antigen b. Helper T cells—produce memory T cells c. The memory T cells—cause a secondary response if the same antigen enters the body again d. Suppressor T cells—release substances that shut down killer T cells after the pathogenic cells brought under control.

Antibody Structure Transplants Shaped like the letter Y Has 2 identical antigen-binding sites Small differences in the amino acids affect the shaped of the binding sites; make antibody the ability to recognize to an antigen with a complementary shape

Transplant T cells make acceptance of organ transplants difficult. Rejection- immune system damages and destroys the transplanted organ Donors sought whose cell markers nearly identical to cell markers of recipient Recipients take drugs to suppress the cell-mediated immune response

Acquired Immunity Active Immunity 1. Vaccination- the injection of weakened or mild form of pathogen to produce immunity. 2. Edward Jenner credited w/1 st vaccination for smallpox 3. Vaccines stimulate the immunity system to produce millions of plasma cells ready to produce specific types of antibodies 4. More than 20 serious human diseases have vaccine 5. Occurs after exposure to an antigen 6. May result from natural exposure to an antigen or from deliberate exposure to the antigen.

Passive Immunity 1. Produced when antibodies from other animals against a pathogen are injected into bloodstream. 2. Lasts only a short time b/c the body eventually destroys the foreign antibodies 3. Can develop naturally or by deliberate exposure Ex: passing of antibodies from mother to fetus in development or in early infancy via breast milk  protects a child from many infectious diseases for many months

Immune System Disorders I. Allergies  overreactions of the immune system to antigen.  Common allergens: pollen, dust,mold & bee stings.  Mast cells-specialized immune system cells that initiate the inflammatory response and release histamines.  Histamines- chemicals released by activated mast cells - increase flow of blood and fluids to surrounding area and increase mucus production.  Antihistamines- drugs that are used to counteract the effects of histamines.

II. Asthma a chronic respiratory disease in which the air passages become narrower than normal. Heredity and environmental factors ( pollution, smoke) a leading cause of serious illness among children (life- threatening) An asthmatic attack triggered by emotional stress, pollen, cold air, certain medication, respiratory infection, tobacco smoke etc. No cure, but some medications relax the smooth muscles around the airways, making breathing easier.

Autoimmune Diseases  Cause- when the immune system makes a mistake and attacks the body’s own cells.  “anti-self” antibodies  Ex: Type I Diabetes, rheumatoid arthritis, myasthenia gravis and multiple sclerosis(MS)  Some are treated with medication that alleviate symptoms.  Ex: insulin injection- Type I Diabetes and some medications that suppress the immune response

AIDS ( Acquired Immune Deficiency Syndrome)  2 types- immune system fails to develop normally and AIDS-results from a viral infection that destroy helper T cells.  HIV-retrovirus that causes AIDS.  HIV attacks Key T cells in the immune system, destroying the body’s defense.  when HIV virus attacks a helper T cell, it attaches on the cell membrane- once inside, the virus forces the host cell to make DNA copies of its RNA, then the new virus leaves the T cell and destroys more.  HIV can be transmitted by (Sexual intercourse, shared needle, contact with blood/products and from mother to child during pregnancy, nursing.)with an infected person  the only prevention is ABSTINENCE  No cure, but currently multidrug and multivitamin "cocktails” can fight the virus.