The Immune System. I. Source of Infection Pathogen - microorganism that causes disease Ex: bacteria,...

The Immune System

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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



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







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





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





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


• Antibody - a protein produced in

response to a particular

antigen that will target &

destroy only that particular

antigen (foreign substance)


• 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*


B. Killer T cells: lymphocytes processed in the thymus that produce powerful chemicals that destroy infected body cells = “bomber cells”




C. B Cells: lymphocytes produced in the bone marrow that make antibodies


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



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

The Immune System. I. Source of Infection Pathogen - microorganism that causes disease Ex: bacteria,...

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