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Immune System
Our defense system against
the little guys.
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Disease
Any change, other than injury, that disrupts normal body functions
Can be caused by agents or pathogens, environmentally, or are inherited
What are some examples of pathogens?
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Pathogens Viruses Bacteria Protists Parasites (worms) Fungi
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Diseases Spread
Physical contact Direct contact with bodily fluids Indirect through air from coughing or
sneezing or touching contaminated objects
Contaminated Food and Water Infected Animals
Vectors: animals that carry pathogens Example: Lyme disease and the deer tick
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Immune System
Functions to fight infections through the production of cells that inactivate foreign substances or cells = immunity
Body fights infection:
1. Nonspecific Defense
2. Specific Defense
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Nonspecific Defense
First line of Defense: Keep pathogens out of body. Prevent infection. Skin, mucus, sweat, tears,
stomach acid. Second line of Defense:
Inflammatory response Mast cells release Histamines. WBC’s, phagocytes, drawn in. Fever (kills microorganisms) Swelling, redness Pus
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Skin Wound
Bacteria enter the wound
Phagocytes move into the area and engulf the bacteria and cell debris
Capillary
The Inflammatory ResponseThe Inflammatory Response
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Specific Defense
Immune response:Pathogen, or antigen, gets past
nonspecific defenseLymphocytes recognize specific
antigens: B cells - humoral immunity T cells - cell-mediated immunity
Macrophages: bring antigens to the T-cells from the pathogen they ingest.
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Humoral Immunity
Antibody mediated immunity1. Antigen recognized by specific B cell2. B cells produce large #’s of plasma B
and memory B cells3. Plasma B cells release antibodies4. Antibodies bind to antigen5. Memory B cells prevent another
infection.6. Takes place in the fluids (humors).
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Antigen-binding
sites
Antigen Antibody
Structure of an Antibody
Antibodies:
Proteins that
recognize & bind to specific antigens.
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Cell-Mediated Immunity
Once the pathogen is inside cell:
1. Cell signals infection to Helper T cell.
2. Helper T cell can activate BOTH Killer T cells and Plasma B cells
3. Killer T cells kill infected body cells.
4. Memory T cells are produced after exposure.
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Acquired Immunity
Active Immunity: Body’s produces antibodies to an antigen. Vaccination = injection of weakened or
mild form of pathogen causes antibody production
Passive Immunity: Antibodies produced by another organism
injected into bloodstream Lasts short time Antibodies from mom or mother’s milk.
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What happens when things go wrong?
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Allergies
Allergies are the “overreaction” of the bodies immune system to microorganisms, like pollen or animal dander.
The bodies mast cells release histamines, because of the increase of blood and fluids to the area, we experience a runny nose and watery eyes.
Allergies can be either genetic or environmentally caused.
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Asthma
Narrowing of the air passages by the spasm contractions of the smooth muscle.
Chronic disease Reaction to antigens
or stress related. Both hereditary and
environmental causes.
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Autoimmune disorders
Autoimmune disorders are when the body attacks itself.
It has lost the ability to recognize its own cells. No sense of “self”.
Diseases like Type I Diabetes, Rheumatoid arthritis, Lupus and Multiple sclerosis (MS) are common autoimmune disorders.
Lupus rash
RA
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Koch’s Postulates
The pathogen should always be found in the body of a sick organism and should not be found in a healthy one.
The pathogen must be isolated and grown in the laboratory in a pure culture.
When purified pathogens are placed in a new host, they should cause the same disease that infected the host.
The very same pathogen should be re-isolated from the second host. And it should be the same as the original pathogen