I. Source of Infection• Pathogen - microorganism that causes
disease
Ex: bacteria, virus, yeast, fungus,
protists, parasitic worms, etc.
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SOURCE EXAMPLES HOW SPREAD
PREVENTION
Direct human contact
Objects (vectors)
Airborne
Water
Food
Arthropod bites
II. Non-Specific Defenses (Innate Immunity)
A. Physical Defenses
1. First line of defense = skin, an
impermeable barrier that keeps
pathogens out
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II. Non-Specific Defenses2. Defenses that protect natural body openings:
mucus - traps microbes & prevents tissues from drying out
saliva - wash surface of teeth; contain lysozymes, enzymes which break down bacteria
tears - lubricate surface of eyes & contains lysozyme
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II. Non-Specific DefensesB. Chemical defenses
1. Stomach acid: destroys many swallowed pathogens
2. Complement: group of blood proteins that attach to pathogens & help destroy them
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II. Non-Specific DefensesB. Chemical defenses
3. Phagocytes: white blood cells that ingest & destroy pathogens (“pac-man” cells)
4. Interferon: a protein substance that interferes with viral replication
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II. Non-Specific Defenses5. Inflammation: damaged cells
release histamine, which dilates blood vessels & increases tissue fluid in the injured area (swelling); this attracts phagocytes which release proteins that increase body temperature (fever) in order to inhibit the growth of pathogens & speed up the rate of tissue repair
III. Specific Defenses Against Disease
• Immunity - resistance to a specific
pathogen or substance
• Antigen - a substance capable of
stimulating a specific immune
response - recognized as
“foreign” by the body
III. Specific Defenses Against Disease
• Antibody - a protein produced in
response to a particular
antigen that will target &
destroy only that particular
antigen (foreign substance)
III. Specific Defenses Against Disease
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III. Specific Defenses Against Disease
• Types of Lymphocytes (White Blood Cells that help defend the body)
A. Helper T cells: lymphocytes processed in the thymus that identify the invading antigen & signal the immune system to activate B cells = “guard cells”
*type of cell targeted by the HIV virus*
III. Specific Defenses Against Disease
B. Killer T cells: lymphocytes processed in the thymus that produce powerful chemicals that destroy infected body cells = “bomber cells”
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III. Specific Defenses Against Disease
C. B Cells: lymphocytes produced in the bone marrow that make antibodies
III. Specific Defenses Against Disease
D. Memory Cells: cells that are made during an immune response but are kept in storage for a future attack by the same antigen - these cells contain the “recipe” for making a specific type of antibody
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Passive vs. Active ImmunityPassive Immunity• Develops when antibodies are received
(given to you)
• Natural: from mother through placenta or breast milk• Artificial: injection of gamma globulins ex: anti-venom (antibodies)
• Temporary: lasts for a few weeks
• Fast: works almost immediately
Passive vs. Active ImmunityActive Immunity• Develops when antibodies are made in your own body
• Natural: pathogen (germ) exposure• Artificial: vaccine
• Long lasting: months - years or permanent
• Slow: takes several weeks to develop & may require a booster to form enough memory cells