The Immune System

I. Source of Infection Pathogen - microorganism that causes disease Ex: bacteria, virus, yeast, fungus, protists, parasitic worms, etc.

SOURCEEXAMPLESHOW 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 Defenses 2. 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 Defenses B.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 Defenses B.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 Defenses 5. 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

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”

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

Passive vs. Active Immunity Passive 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 Immunity Active 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

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