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Innate defenses
- First line of defense
- Found in all animals
- Includes: skin, mucous membranes, phagocytic cells, antimicrobial proteins
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Invertebrates have:
Innate immunity
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Vertebrates have:
Innate AND acquired immunity
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Interferons
- Proteins produced by virus infected cells
- Found only in vertebrates
- Help other cells resist viruses
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Inflammatory response
- Triggered by tissue damage
- Disinfects tissues
- Limits further infection
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Lymphatic system
A network of lymphatic vessels and organs
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Lymphatic vessels
- Collect fluid from body tissues
- Return is as lymph to the blood
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Lymph organs
- Such as the spleen and lymph nodes
- Packed with white blood cells that fight infections
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Antigens
Foreign molecules
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Active immunity
Triggered by infection or vaccinations
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Passive immunity
Can be temporarily acquired by receiving premade antibodies
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B cells
- Secret antibodies
- Mount the humoral immune response
- Bacteria and viruses
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T cells
- Attack cells infected with bacteria or virus
- Cell-mediated immune response
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Two kinds of lymphocytes
B cells and T cells
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Antigenic determinants
- Specific regions on an antigen
- To which antibodies bind
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Clonal selection
Musters defensive forces against specific antigens
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Steps of clonal selection
- Primary immune response
- Secondary immune response
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Primary immune response
- Produces effector cells
- Memory cells that may confer lifelong immunity
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Antibodies
Secreted by plasma (effector) B cells into the blood and lymph
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Antibody molecule
- Y-shaped
- Two antigen binding sites
- Specific to the antigenic determinants
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Helper T cells and cytotoxic T cells
- Primarily responsible for the cell-mediated immune response
- Helper T cells also stimulate the humoral response
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AIDS (Acquired Immunodeficiency Syndrome)
- Results from infection by HIV (human immunodeficiency virus)
- Attacks helper T cells
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The immune system normally reacts:
- Only against nonself substances
- Not against self
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Transplanted organs:
- Can be rejected by the body
- Donors are used that most closely match the patients tissues
- Transplants between identical twins don't usually have this problem
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Autoimmune disease
- The immue system turns against the body's own molecules
- Examples include: Lupus, rheumatoid arthritis, Insulin-dependant diabetes mellitus, Multiple sclerosis
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Immunodeficiency diseases
- Immune components are lacking
- Recurrent infections are frequent
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The immune system may be weakened by:
- Physical stress
- Emotional stress
- Students are more likely to be sick during the week of finals
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Allergies
Hypersensitive (exaggerated) responses to antigens (allergens) in our environment
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Allergic rxns typically occur:
Very rapidly in response to tiny amounts of an allergen
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Parts of the body where allergic rxns occur:
- Nasal passages
- Bronchi
- Skin
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Antihistamines
- Interfere with histamine's action
- Provide temporary relief
- Often make people drowsy
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Anaphylactic shock
- Extreme, life-threatening allergic rxn
- Can be treated with injections of epinephrine
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