The Immune System and Disease                                             

Infectious Disease What is a disease? Any change, other than an injury, that disrupts the normal functions of the body. Some diseases are produced by pathogens, such as bacteria, viruses, and parasites. Others are caused by materials in the environment, such as cigarette smoke. Still others, such as hemophilia, are inherited.

The Germ Theory of Disease Louis Pasteur and Robert Koch Infectious disease caused by microorganisms Koch Pasteur

Agents of Disease Viruses Bacteria Protists Worms Fungi Influenza and Warts Bacteria Botulism and Anthrax Protists Malaria and African Sleeping Sickness Worms Schistosoma and Tapeworms Fungi Athlete’s foot and Ringworm

How Bacteria Produce Disease Some bacteria damage the cells and tissues of the infected organism directly by breaking down the cells for food. Others release toxins, which are poisons that travel throughout the body and interfere with the normal activity of the host.

Diseases Caused by Bacteria Lyme disease Tetanus Tuberculosis Anthrax Bacterial meningitis Strep throat Salmonellosis Tooth decay

Preventing Bacterial Disease Many bacterial diseases can be prevented with vaccines. Vaccines are preparations of weakened or killed pathogens used to produce immunity to the disease. If infection does occur, antibiotics are used to block the growth and reproduction of bacteria.

Penicillin and Bacteria The cell wall of a bacterium is made of sugars and amino acids Penicillin stops the enzyme that links the sugar chains Holes develop in the cell wall, the bacterium ruptures and dies

Controlling Bacteria Most bacteria are harmless and many are beneficial, but efforts are still made to control bacterial growth in order to reduce the risk of infection. Sterilization by heat Disinfectants like soap and chemicals (overuse can lead to resistant strains) Refrigeration, cooking, and canning of foods

Viral Disease Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium. Viral diseases cannot be treated with antibiotics. The best protection from viruses is prevention of disease, especially vaccination.

Diseases Caused by Viruses Common cold Influenza Smallpox Warts AIDS Chickenpox Measles Ebola West Nile Polio

Viral Disease in Plants Viruses that infect plants threaten many agricultural crops. Viruses have a hard time entering plant cells because of the cell wall. Most plant viruses are adapted to take advantage of small breaks in the cell wall. Insects are also responsible for spreading plant viruses as they feed on plants.

How Diseases are Spread Physical Contact Direct: shaking hands, sex Indirect: through the air or on objects Contaminated Food and Water Infected Animals (Vectors)

The Immune System The immune system is the body’s defense against pathogens (“Sickness-makers”) The immune system recognizes, attacks, destroys and remembers each type of pathogen that enters the body. The function of the immune system is to fight infection through the production of cells that inactivate foreign substances or cells. This process is called immunity.

Defense Level 1—Barriers Barriers, which physically block pathogens from entering the body are the first line of defense. Skin, hair, mucus, sweat, tears, coughing, sneezing, and stomach acids

Defense Level 2—Nonspecific Innate Immune Response is a rapid response to all pathogens in the same generalized way Inflammation—increased blood flow delivers defense molecules Phagocytes—white blood cells Complement System—proteins coat pathogens

Defense Level 3—Antibodies Adaptive Immune Response—slower, acquired defense dependent on the recognition of specific pathogens Recognition of antigens on the surface of pathogens Antibodies bind to and inactivate antigens Once the body has been exposed to a pathogen, memory B cells remain capable of producing antibodies to it.

Defense Level 3—T Cells When pathogens get inside cells, antibodies alone cannot kill them. T cells kill or help kill antigens T cells are a problem with transplants, and drugs must be taken to prevent rejection.

Acquired Immunity Active Immunity—produced by the body’s reaction to a vaccine or infection Passive Immunity—antibodies produced by another animal are injected or passed from mother to child, lasts a short time

Acquired Immunity

Immune System Disorders

Allergies Overreaction of the Immune System                                Overreaction of the Immune System Antigens that cause allergic response are called allergens. Histamines released cause sneezing, watery eyes, and other irritations

Autoimmune Diseases The immune system makes a mistake and attacks the body’s own cells. Type I diabetes—insulin-producing cells Rheumatoid arthritis—connective tissue Myasthenia gravis—neuromuscular junctions Multiple sclerosis—neurons in brain and spinal cord

AIDS an Immunodeficiency Disease HIV infection destroys helper T cells causing the immune system to break down. Acquired Immune Deficiency Syndrome Opportunistic diseases attack

Transmission of HIV AIDS is deadly, but it is NOT easily transmitted! ANY form of sexual intercourse Shared needles or syringes Contact with blood or blood products From mother to child during pregnancy or breastfeeding It is NOT transmitted by casual contact (i.e. shaking hands, hugging, kissing on the cheek)

Preventing HIV Infection The only no-risk behavior with respect to HIV and AIDS is abstinence. Avoid drug use and contaminated needles. Transmission through blood transfusions has been nearly eliminated due to screening of the blood supply and discouraging potentially infected individuals from donating.

Can AIDS Be Cured? At present, there is no cure for AIDS. Multidrug and multivitamin “cocktails” make it possible for people to survive HIV infection for years.                                                                  

What About a Vaccine? No vaccine is available due to the rapid rate of HIV virus mutation. The AIDS Memorial Quilt The total number of deaths from AIDS worldwide is now more than 35 million people.