Immune System and Disease Chapter 35 Infectious Disease

Immune System and Disease Chapter 35

Infectious Disease Causes: Germ Theory of Disease • Led by Louis Pasteur (French) and Robert Koch (German) bacteriologist Infectious Disease – Occurs when microorganisms cause physiological changes that disrupt normal body functions

Agents of Disease Infectious diseases can be caused by viruses, bacteria, fungi, “protist” and parasites. Pathogens – disease – causing microorganisms; except parasites

Agents of Disease Viruses • Characteristics • Nonliving • Replicate by inserting their genetic material into a host cell and taking over many of the host cell’s function • Diseases • • Common cold Influenza Chicken pox Warts

Agents of Disease Bacteria • Characteristics • Break down the tissues of an infected organism for food or release toxins that interfere with normal activity in the host • Disease • • Streptococcus infection (Strept Throat) Diphtheria Botulism Anthrax

Agents of Disease Fungi • Characteristics • Cause infections on the surface of the skin, mouth, throat, fingernails, and toenails. • Dangerous infection may spread from lungs to other organs • Disease • Ringworm • Thrush

Agents of Disease “Protists” • Characteristics • Single-celled Eukaryotes may infect people through contaminated water and insect bites • They take nutrients from their host • Most inflict damage to cells and tissue • Disease • Malaria • African Sleeping Sickness • Intestinal Diseases

Agents of Disease Parasitic Worms • Characteristics • Most that infect humans are wormlike • May enter through the mouth, nose, anus, or skin • Most reside in the intestinal tract where they absorb nutrients from the host • Diseases • • Trichinosis Schistosomiasis Hook worm Elephantiasis

How Diseases Spread Pathogens often spread by the symptoms of the actual disease Sneezing, coughing, or diarrhea Natural selection favors the pathogens with adaptations that help them spread from host to host

Coughing, Sneezing, and Physical Contact Usually bacteria or viruses that infect the nose, throat, or respiratory tract Spread by indirect contact Coughing and sneezing releases thousands of tiny droplets that can be inhaled by other people Droplets can settle on objects, you touch them then touch your nose or mouth

Coughing, Sneezing, and Physical Contact Pathogens like staphylococci (staph) are drug resistant and are transferred by body to body contact or by towel or sports equipment Prevention

Exchange of Body Fluids Sexual Transmitted Disease – pathogens transmitted by sexual activity, need direct contact from body to body Include: • • Herpes Gonorrhea Syphilis Chlamydia

Exchange of Body Fluids Other pathogens need blood to blood contact often seen with IV drug user Hepatitis HIV can be both transmitted by both blood and sexual contact.

Contaminated Water or Food Many pathogens that infect the digestive tract are spread through the water contaminated by feces from infected people or animals Symptoms of these diseases include diarrhea Adaptation that helps spread pathogen Contaminated water can be consumed or spread on fruits or vegetables Prevention is as simple as washing foods

Contaminated Water or Food Bacteria can be present in seafood and uncooked meat Cooking properly can prevent diseases caused by these pathogens

Zoonosis: The Animal Connection Zoonosis – any disease that can be transmitted from animals to humans • Mad Cow Disease • SARS (Severe Acute Respiratory Syndrome) • West Nile Virus • Lyme Disease • Ebola • Bird Flu

The Animal Connection Vectors – a carrier of a pathogen that transports the pathogen but does not get sick itself • Infection can also occur when a person is bitten by an infected animal • Consumes the meat of an infected animal • Come in close contact with an infected animal’s waste or secretions

Defense Against Infection Nonspecific Infection • 1 st Line of Defense • Skin – widespread physical barrier • Saliva, mucus, and tears protect openings such as mouth, nose, and eyes • Lysozyme - an enzyme contained in saliva mucus and tears • Break down bacterial cell walls • Stomach secretions destroy many swallowed pathogens

Defense Against Infection • 2 nd Line of Defense • Inflammatory Response • Infected area become red and painful or inflamed • Response begins when pathogens stimulate cells called Mast Cells • Mast Cells release chemicals known as Histamines

Defense Against Infection • 2 nd Line of Defense Histamines • Increase blood flow and fluids to the affected area • Causes swelling in the infected area • White blood cells move in Phagocytes – engulf and destroy bacteria • All the above causes an increase in temperature in the area

Defense Against Infection • 2 nd Line of Defense Interferons • Proteins (produced by host cells) that inhibit synthesis of viral proteins • This is a way of “buying time” for a specific immune response

Defense Against Infection • 2 nd Line of Defense Fever • Increased body temperature slows down or stops the growth of some pathogens • Also speeds up the immune response • Fever caused by chemicals released by immune system

Specific Defenses: The Immune Response Responds to particular pathogens Recognizing “Self” • A healthy immune system recognizes all cells and proteins that belong in the body; as self Recognizing “Nonself” • The immune system recognizes foreign organisms and molecules as other or “nonself”. • Once recognized as “nonself” it uses cellular and chemical weapons to attack them

Specific Defenses: The Immune Response – after an encounter with specific invader the immune system remembers it • This enables a more rapid response if invaded by the same pathogen

Specific Defenses: The Immune Response Antigens – any foreign substance that can stimulate an immune response • Located on the outer surface of bacteria, viruses, or parasites • The immune system response to antigens by: 1. Increase the number of cells the either attack the invader directly 2. Produce antibodies • Proteins that “tag” antigens for destruction

Specific Defenses: The Immune Response Lymphocytes B Lymphocytes (B Cells) • Produced and mature in red bone marrow T Lymphocytes (T Cells) • Produced in bone marrow but mature in thymus • Each recognizes one specific antigen • Our gene determine particular B/T Cells • When mature both types of cells travel to lymph nodes and spleen, where they encounter antigens

The Immune System in Action Humoral Immunity • Activated when antibodies embedded on a few existing B cells bind to antigens on the surface of invading pathogen • When an antigen binds to an antibody carried by a B Cell, T Cells stimulate B Cells to grow and divide rapidly • B Cells of 2 types are produced: 1. Plasma Cells • Produce and release antibodies that are carried through the blood stream • These antibodies recognize and bind to free floating antigens or surfaces of pathogens

The Immune System in Action 2. Memory B Cells • Plasma cells die after an infection • Some B Cells that would recognize the same antigen remain alive B Cells produce new plasma cells to battle returning pathogen • Very fast; provides long-term immunity • Immune memory is the reason vaccinations work •

Cell-Mediated Immunity This part of the immune system defends the body against some viruses, fungi, and singlecelled pathogens Depends on macrophages and T Cells also helps the body from cancer cells Macrophages consume a pathogen A portion of antigen is out Helper T Cells activate B Cells which activate Cytotoxic T Cells.

Cell-Mediated Immunity Cytotoxic T Cells – hunts down body cells infected with a particular antigen and kill the cells Suppressor T Cells – helps keep immune system in check • Stops or slows response once infection is controlled • May also be involved in auto-immune reponse

Cell-Mediated Immunity Cytotoxic T Cells make organ transplants difficult A transplanted organ is marked as “nonself” T Cells and proteins would damage and destroy the transplanted organ To prevent rejection doctors search for cell markers that are identical to cell markers of the recepient

Fighting Infectious Disease Acquired Immunity Vaccination - the injection of a weakened form of a pathogen or of a similar but less dangerous pathogen to produce immunity

Fighting Infectious Disease Passive Immunity • Antibodies produced against a pathogen by other individuals or animals can be used to produce temporary immunity • Usually last only a short time because the immune system eventually destroys foreign antibodies • Can occur naturally: • Like from pregnant woman to fetus; across placenta or breast milk

Immune System Disorders A strong immune response to harmless antigens can produce allergies, asthma, and autoimmune disease Allergies – when allergens enter the body and trigger an inflammatory response by causing most cells to release histamines • If it occurs in the respiratory system it increases mucous production and causes; sneezing, watery eyes, a runny nose, etc Antihistamines – a drug that helps response by reversing histamine reaction.

Immune System Disorders Asthma – a chronic disease in which air passages narrow, causing wheezing, coughing, and difficulty breathing • Can be both caused by heredity and/or environmental factors

Immune System Disorders Autoimmune Disease • When the immune system attacks the body’s own cells • Type I Diabetes – antibodies attack insulin-producing cells in the pancreas • Rheumatoid Arthritis – antibodies attack tissue around joints • Lupus – antibodies attack organs and tissues causing areas of chronic inflammation though out the body

Immune System Disorders Lupis Rheumatoid Arthritis

Immune System Disorders Opportunistic Disease – A disease that attacks a person with weakened immune system. AIDS – Acquired Immunodeficiency Syndrome HIV – the cause of AIDS; • Human Immunodeficiency virus

Immune System Disorders HIV is deadly for two reasons: 1. It can hide from the defenses of the immune system 2. Attacks key cells within the immune system • HIV is a retrovirus • A Retrovirus carries its genetic material into the cell • The T Cell is HIV’s main target

Immune System Disorders Transmission – only through infected blood, semen, vaginal secretions, or breast milk • Four Main ways HIV is transmitted: 1. Sexual intercourse 2. Sharing needles 3. Contact with infected blood products 4. From infected mother to her child during pregnancy, birth, or breast feeding

Immune System Disorders Only no-risk behavior with HIV transmission is abstinence from sexual activity and IV drug use No cure but a new variety of drugs makes it possible to survive