The Immune System and Disease It’s you against the world…

What is a disease?  A disease is any change, other than an injury, that disrupts the normal functions of the body.  Some diseases are caused by pathogens, or “sickness-makers”. These are generally called infectious diseases.  Pathogens can be bacteria, viruses, materials in the environment, etc.  Other diseases can be hereditary.  A disease is any change, other than an injury, that disrupts the normal functions of the body.  Some diseases are caused by pathogens, or “sickness-makers”. These are generally called infectious diseases.  Pathogens can be bacteria, viruses, materials in the environment, etc.  Other diseases can be hereditary.

The Germ Theory of Disease  The idea that infectious diseases are caused by microorganisms of different types, or germs.

Koch’s Postulates  Pathogen should always be found in a sick individual  Must be able to isolate pathogen and grow in culture in lab.  When placed in new hosts, pathogen should cause same disease as original individual  When isolated from second host, pathogen should be identical to original pathogen.  Pathogen should always be found in a sick individual  Must be able to isolate pathogen and grow in culture in lab.  When placed in new hosts, pathogen should cause same disease as original individual  When isolated from second host, pathogen should be identical to original pathogen.

Agents of Disease  For many pathogens, the human body is the perfect environment for growth - warm, dark and moist with an abundance of nutrients

Viruses  Tiny particles that invade and replicate in cells  Can infect nearly every type of organism  Tiny particles that invade and replicate in cells  Can infect nearly every type of organism

Bacteria  Cause disease by either breaking down tissue for food or releasing toxins that harm the body

Protists  Unicellular eukaryotes that usually exist independently or in colonies and are not usually associated with disease  Plasmodium - a protist that causes malaria  Trypanosoma - causes African sleeping sickness  Unicellular eukaryotes that usually exist independently or in colonies and are not usually associated with disease  Plasmodium - a protist that causes malaria  Trypanosoma - causes African sleeping sickness

Worms  Flatworms and roundworms are responsible for many human diseases  Schistosoma  Tapeworms  Hookworms  Flatworms and roundworms are responsible for many human diseases  Schistosoma  Tapeworms  Hookworms

Fungi  Most are harmless - mushrooms  Some cause serious problems  Tinea pedis - athlete’s foot  Most are harmless - mushrooms  Some cause serious problems  Tinea pedis - athlete’s foot

How are diseases spread?  Physical Contact  Direct  indirect  Contaminated food and water  Food poisoning  Fecal-oral  Infected animals  Animals, such as mosquitos and ticks, can be vectors for disease.  Physical Contact  Direct  indirect  Contaminated food and water  Food poisoning  Fecal-oral  Infected animals  Animals, such as mosquitos and ticks, can be vectors for disease.

The Lymphatic System

How do we fight disease?  Antibiotics  Compounds that kill bacteria without harming the infected host cells.  Work by interfering with cellular processes of bacteria  Not effective against viruses  Over-the-counter drugs  Treat only the symptoms  Antibiotics  Compounds that kill bacteria without harming the infected host cells.  Work by interfering with cellular processes of bacteria  Not effective against viruses  Over-the-counter drugs  Treat only the symptoms

The Immune System  The Immune System is the body’s way of fighting infection through Immunity - the production of cells that inactivate foreign substances or cells.

Non-Specific Defenses  First line of defense - keep pathogens out of body  Skin, mucus, sweat, tears  Second line of defense  Inflammatory response - nonspecific defense reaction to tissue damage caused by injury or infection  Fever - A release of chemicals that increase the body’s core temperature.  Slows down or stops growth of pathogens  Increases heart rate to get white blood cells to infection faster  Interferons - proteins that interfere with the growth of viruses  First line of defense - keep pathogens out of body  Skin, mucus, sweat, tears  Second line of defense  Inflammatory response - nonspecific defense reaction to tissue damage caused by injury or infection  Fever - A release of chemicals that increase the body’s core temperature.  Slows down or stops growth of pathogens  Increases heart rate to get white blood cells to infection faster  Interferons - proteins that interfere with the growth of viruses

Specific Defenses  If a pathogen is able to get past the non-specific defenses of the body, the immune system responds with an immune response - a series of specific defenses that attack a particular disease causing agent.  Antigen - a substance that triggers this response  If a pathogen is able to get past the non-specific defenses of the body, the immune system responds with an immune response - a series of specific defenses that attack a particular disease causing agent.  Antigen - a substance that triggers this response

Humoral Immunity  When a pathogen invades the body, its antigens are recognized by B lymphocytes (B cells) which divide and produce large numbers of B cells and plasma cells  Plasma cells release antibodies, which bind to antigens  Once exposed to a pathogen, millions of B cells remain capable of producing antibodies specific to that pathogen.  When a pathogen invades the body, its antigens are recognized by B lymphocytes (B cells) which divide and produce large numbers of B cells and plasma cells  Plasma cells release antibodies, which bind to antigens  Once exposed to a pathogen, millions of B cells remain capable of producing antibodies specific to that pathogen.

Antibody Structure

Cell-Mediated Immunity  Viruses and other pathogens cannot be destroyed by antibodies alone  The body’s primary defense against its own cells when they become infected.  Also important in fighting fungi and protists  Viruses and other pathogens cannot be destroyed by antibodies alone  The body’s primary defense against its own cells when they become infected.  Also important in fighting fungi and protists

Acquired Immunity  Active Immunity - appears after exposure to an antigen  Vaccination - the injection of a weakened form of a pathogen to produce immunity  Passive Immunity - antibodies against a pathogen which are produced by other animals are injected into the bloodstream  Short-term. Body destroys foreign antibodies  Active Immunity - appears after exposure to an antigen  Vaccination - the injection of a weakened form of a pathogen to produce immunity  Passive Immunity - antibodies against a pathogen which are produced by other animals are injected into the bloodstream  Short-term. Body destroys foreign antibodies

Immune System Disorders  Allergies  Asthma  Autoimmune diseases  AIDS  Allergies  Asthma  Autoimmune diseases  AIDS

Preventing the Spread of Infectious Disease  Chain of Transmission  Reservoir  Portal of exit  Means of transmission  Portal of entry  Susceptible host  Hand washing  Cover your cough  Healthy diet  Exercise and rest  Just say no  See the doctor  Chain of Transmission  Reservoir  Portal of exit  Means of transmission  Portal of entry  Susceptible host  Hand washing  Cover your cough  Healthy diet  Exercise and rest  Just say no  See the doctor