Infectious Disease & The Immune System

Disease Disease – any change, other than injury, that disrupts the normal functions of the body Some diseases are produced by agents (bacteria, viruses, etc.), some are environmental and some are inherited Pathogens – disease-causing agents; “sickness-makers”

Agents of Disease Viruses (Common Cold, Influenza (flu)) Bacteria (Strep, Botulism, Anthrax) Protists (Plasmodium (causes Malaria), Amebic dysentery) Worms (Tapeworms, Hookworms) Fungi (Ringworm, Athlete’s Foot)

How are Diseases Spread Physical Contact –Direct – Touching –Indirect – Sneezing or Coughing Contaminated Food & Water Infected Animals

Fighting Infectious Diseases Antibiotics – compounds that kill bacteria –Only work on bacterial infections, no effect on viruses Over-the-Counter Drugs –Can treat the symptoms of the disease and make you feel better, but they do not treat the cause of the disease – you need your Immune System for that

The Immune System Body’s main defense against pathogens It recognizes, attacks, destroys and “remembers” each type of pathogen that enters the body Does this by producing specialized cells that inactivate pathogens – there is a specific cell produced for each pathogen

Two Categories of Defense 1. Nonspecific Defenses –Guard against the infections by keeping most things out of the body 2. Specific Defenses –Track down harmful pathogens that have broken through the body’s nonspecific defenses

Nonspecific Defenses Helps keep pathogens out of the body Most important nonspecific defense is the skin Mucus, sweat and tears also help in this process If pathogens do manage to enter the body (ex. cut), then white blood cells are produced to destroy the pathogen

Specific Defenses If a pathogen can get past the body’s nonspecific defenses, then the immune system reacts with a series of specific defenses to attack the invader A substance that triggers this response is known as an antigen –Viruses, bacteria and other pathogens serve as antigens that trigger the immune system response

Specific Defenses, cont. Most common response is that Antibodies are produced Antibodies are proteins that recognize and bind to antigens Once the body has been exposed to a pathogen, the body maintains the ability to produce those specific antibodies again at any time

Picture of an Antibody Antibodies are shaped like a Y Shapes of the binding sites are different on each antibody in order to recognize a large variety of antigens

Specific Defenses, cont. Whenever the body’s own cells are infected with a virus or become cancerous, antibodies alone cannot destroy them This is where T cells are needed to help fight these kind of infections

Immunity How do you get immunity to diseases? 1. Natural Exposure to an antigen – –You have a disease and fight the infection off 2. Deliberate Exposure – –Vaccination – injection of a weakened or mild form of a pathogen; used today to prevent more than 20 serious human diseases

Immune System Disorders Allergies – overreaction to dust, pollen, mold, bee stings, etc. Asthma – chronic respiratory disease in which the air passages become narrower than normal Autoimmune Diseases – when the immune system makes a mistake and attacks the body’s own cells; ex. Type I diabetes and Multiple Sclerosis (MS)

Immune System Disorders, cont. AIDS (Auto Immune Deficiency Syndrome) –Results from a viral infection (HIV) that destroys the T cells of the immune system –Leaves the body with no protection against other pathogens –HIV can be spread by sexual contact, sharing needles during drug use, contact with blood or blood products of an infected person & from infected mother to child –No cure at this time, but there are many drugs that can prolong the life of someone with HIV/AIDS

Immune System Video Clip