The Immune System Chapter 40

Agents of Disease The human body provides a suitable environment for many microorganisms: it is moist, warm and full of nutrients. Not all microorganisms are harmful; some are beneficial. Bacteria living in the intestines aid in digestion. Microorganisms that cause disease are called pathogens. Agents of disease include viruses, bacteria, protists, worms, fungi, arachnids and insects.

Infectiously Cute Plush Microbes!

Pathogens and Disease Section 40-1 Pathogen Types Disease Agent That Causes Disease Method of Transmission Common cold Rhinovirus Two types (A, B), plus subtypes Varicella Paramyxovirus Mycobacterium tuberculosis Neisseria meningitidis Vibrio cholerae Clostridium tetani Trypanosoma Plasmodium Entamoeba histolytica Schistosoma Taenia saginata Imperfect fungi Airborne; direct contact with infected person Airborne; droplet infection; direct contact with infected person Droplets in air; direct contact with secretions of infected person Droplets in air; contaminated milk and dairy products Direct contact with a carrier Contaminated drinking water Contaminated wound; usually puncture wound Spread by tsetse fly Spread by Anopheles mosquitoes Freshwater streams and rice paddies Contaminated meat Contact with infected person Exchange of hats, combs, or athletic head gear with infected person Viruses Influenza Chickenpox Measles Bacteria Tuberculosis Meningitis Cholera Tetanus Protists African sleeping sickness Malaria Amoebic dysentery Worms Schistosomiasis Beef tapeworm Fungi Athlete’s foot Ringworm

Infectious Disease Diseases caused by pathogens that can be transmitted from one individual to another are called infectious diseases. Methods of transmittal include: Sneezing

Infectious Disease Diseases caused by pathogens that can be transmitted from one individual to another are called infectious diseases. Methods of transmittal include: Sneezing Coughing

Infectious Disease Diseases caused by pathogens that can be transmitted from one individual to another are called infectious diseases. Methods of transmittal include: coughing Sneezing Contaminated food or water

Urban migration and dense populations offer the perfect environment for the spread of microbial pathogens.

Infectious Disease Diseases caused by pathogens that can be transmitted from one individual to another are called infectious diseases. Methods of transmittal include: coughing Sneezing Contaminated food or water Physical contact

Infectious Disease Diseases caused by pathogens that can be transmitted from one individual to another are called infectious diseases. Methods of transmittal include: coughing Sneezing Contaminated food or water Physical contact Infected animals

Fighting Disease….

Antibiotics Sir Alexander Fleming discovered the first antibiotic, penicillin, by mistake.

Antibiotics Antibiotics work by destroying the cell wall of bacteria. They are specific to certain bacteria. They are ineffective against viruses. Overuse of antibiotics has led to resistant strains of bacteria.

Methicillin-resistant Staphylococcus aureus

Vaccines A vaccine is a weakened or dead form of a pathogen or its toxin. Vaccines stimulate the immune system to protect the body against future invasions by the pathogen. The first vaccine was developed by Edward Jenner against the Small Pox virus.

The first vaccination: Edward Jenner used pus from the hand of a dairy maid in 1796 Image: © Bettmann/Corbis

The Immune System First Line of Defense Physical and chemical barriers Skin Secretions Stomach acid

The Immune System Second Line of Defense Inflammatory response – phagocytes Redness, swelling, heat, fever Interferon

Video 1

The Immune System Third Line of Defense The immune response - lymphocytes Antigens (foreign substances) that get past the first and second lines of defense will trigger the production of antibodies by white blood cells. These antibodies are specific for the antigen that caused their formation. Antibodies bind to antigens disabling them.

Structure of an Antibody Section 40-2 Antigen- binding sites Antigen Antibody

Immunity Once activated, the immune system white blood cells “remember” the antigens. Future invasions by the antigen are destroyed immediately by circulating antibodies.

Immune Response Interval between exposures Antibody Concentration Section 40-2 Immune Response Interval between exposures Antibody Concentration First exposure Second exposure Time

Passive Immunity “Borrowed” immunity - the immune system is not activated. Temporary. Antibodies from another source are taken to combat the disease (antibiotics). Eventually the antibodies are recognized as foreign and destroyed.

Active Immunity The immune system is activated and produces antibodies. Lasts a lifetime. Vaccines stimulate active immunity.

Rejection Our tissues contain their own antigens (proteins capable of generating antibodies). Our immune system recognizes these antigens as belonging to ourselves, and does not produce antibodies against them. When a tissue or organ is transplanted, the recipient’s immune system will not recognize it as “self” and will manufactures antibodies to destroy it. This is known as rejection. Drugs are administered to suppress the immune system and lessen this effect.

Immune System Disorders

Immune System Disorders Allergies (a.k.a. immune system gone haywire) The immune system decides certain antigens are deadly …(cat fur, dust, mold, pollen, bee stings, poison ivy) and an inflammatory response is triggered against these allergens. Histamines released by certain cells cause the classic symptoms: watery itchy eyes, runny nose, sneezing, wheezing, coughing, rash….. fun, fun, fun…..

Poison Ivy

Immune System Disorders Asthma An allergic reaction causing the air passageways to narrow therefore restricting breathing. Can be triggered by respiratory infections, exercise, emotional stress, cold air, dust, pollen, dander, and some medications. The tendency towards asthma is inherited.

Immune System Disorders Autoimmune diseases The immune system fails to recognize itself and mistakenly identifies parts of the body as foreign and attacks. Type 1 diabetes Rheumatoid arthritis Multiple sclerosis

Multiple Sclerosis

Immune System Disorders AIDS Acquired Immune Deficiency Syndrome A virus, HIV, destroys key white blood cells involved in the immune response. A person with AIDS does not have a functional immune system. Previous immunity to diseases no longer is effective.