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

The Immune SystemChapter 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!

Viruses

Protists

Worms

Fungi

Disease Agent That Causes Disease

Method of Transmission

Common coldInfluenza

Chickenpox

Measles

Tuberculosis

Meningitis

CholeraTetanusAfrican sleeping sicknessMalariaAmoebic dysenterySchistosomiasisBeef tapewormAthlete’s foot

Ringworm

RhinovirusTwo types (A, B), plus subtypesVaricella

Paramyxovirus

Mycobacterium tuberculosisNeisseria meningitidisVibrio choleraeClostridium tetaniTrypanosoma

PlasmodiumEntamoeba histolyticaSchistosomaTaenia saginataImperfect fungi

Imperfect fungi

Airborne; direct contact with infected personAirborne; droplet infection; direct contact with infected personAirborne; direct contact with infected personDroplets in air; direct contact with secretions of infected personDroplets in air; contaminated milk and dairy productsDirect contact with a carrier

Contaminated drinking waterContaminated wound; usually puncture woundSpread by tsetse fly

Spread by Anopheles mosquitoesContaminated drinking waterFreshwater streams and rice paddies Contaminated meatContact with infected personExchange of hats, combs, or athletic head gear with infected person

Section 40-1

Pathogen Types

Pathogens and Disease

Bacteria

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


•Methods of transmittal include:▫Sneezing▫Coughing

Infectious Disease


•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


•Methods of transmittal include:▫coughing▫Sneezing▫Contaminated food or water▫Physical contact

Infectious Disease


•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.

Antigen-binding

sites

Antigen Antibody

Section 40-2 Structure of an Antibody

Immunity

•Once activated, the immune system white blood cells “remember” the antigens.

•Future invasions by the antigen are destroyed immediately by circulating antibodies.

Interval between exposures

First exposure

Second exposure

Time

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Section 40-2Immune Response

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


•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


•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.


•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


•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.

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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