Playing Defense The Body’s Defense System. External Defenses.
The Body’s Defenses: The Immune System Chapter 43 Part II.
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Transcript of The Body’s Defenses: The Immune System Chapter 43 Part II.
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The Body’s Defenses: The Immune System
Chapter 43Part II
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Two ways to fight
• Innate immunity– Defense before any exposure to pathogen
• Acquired immunity– Defense builds in response to present pathogen
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Specific Defenses
• When nonspecific defense mechanisms are unable to prevent infection, the immune defense system is activated
• Product of immune system that is:1. Specific2. Diverse3. Recognizes self/non-self 4. Able to remember
• May require several days to become fully activated– Deploys extremely powerful cellular and chemical weapons
• Two types of specific defense:– Cell-mediated – Humoral
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1. Specificity
• Response is not random• Recognize and eliminate particular pathogens• Body responds to antigen by releasing
antibody
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Antigens
• Anything that elicits an immune response• Usually a foreign protein• Example: a cat and its dander, an
allergen/antigen for many people
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Antibodies
• Proteins secreted by B cells in response to antigen presence
• Specific antibodies are produced for each antigen type
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2. Diversity
The variable region (V) is different for each antigen!
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3. Self/Non-self Recognition
• Blood groups, tissue grafts, and organ transplants
• Autoimmune disorders – recognition failure
• Major histocompatibility complex (MHC)– Unique proteins embedded in
plasma membrane– Class I
• Cytotoxic T cells
– Class II• Helper T cells
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4. Memory
• Memory cells survive in system for a long period of time
• Activated during secondary immune response
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Immune System Response
• The immune system responds in 3 essential steps:
1. Recognition of the invader (caught on the radar!)
2. Activation of the system (man your battle stations!)
3. Response to the invader (fire all weapons!)
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Once the immune system has been activated…
• The response can be in the form of:– Antibodies (humoral)– Lyphocytes (cell-mediated)
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Humoral Immunity• Activation and clonal
selection of B cells• Secretion of antibodies
to circulate and defend against specific antigens
• Memory cells for secondary response later
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Cell-Mediated Immunity
• Activating and clonal selection of cytotoxic T cells
• Destruction of specific target cells
• Memory cells for secondary response later
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Immune System
• More specific than nonspecific methods
• Memory improves response time when an invader is again encountered
• Immunity can be conferred passively or actively
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Passive Immunity
• Transferred from one individual to another– Antibodies in mother’s milk
• Antibodies can be given to adults as well
• Temporary, jump-start to immunity– Work long enough to prevent
infection
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Active Immunity
• Immunity acquired through individual’s own immune response– Catching a disease
• Vaccinations – Stimulate antibody
production and formation without causing the disease
– Made from killed pathogens or weakened strains
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Passive vs. Active Immunity
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Autoimmune Diseases
• Immune system turns against beneficial molecules in the body
• Ex: lupus– Antibodies break down
histones
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Immunodeficiency Diseases
• Inability of immune system to protect the body• Ex: AIDS– Inability to produce T cells– Can’t stop HIV