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AP Biology 2005-2006 Chapter 43. Immune System lymphocytes attacking cancer cell phagocytic leukocyte lymph system
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AP Biology 2005-2006 Why an immune system? Attack from outside lots of organisms want you for lunch! animals must defend themselves against unwelcome invaders viruses protists bacteria fungi we are a tasty vitamin-packed meal cells are packages of macromolecules no cell wall traded mobility for susceptibility Attack from inside defend against abnormal body cells = cancers
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AP Biology 2005-2006 Key attributes of immune system 4 attributes that characterize the immune system as a whole specificity antigen-antibody specificity diversity react to millions of antigens memory rapid 2° response ability to distinguish self vs. non-self maturation & training process to reduce auto-immune disease
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AP Biology 2005-2006 Lines of defense 1st line: Barriers broad, innate, external defense “barbed wire” skin & mucus membranes 2nd line: Non-specific patrol broad, innate, internal defense “untrained soldiers” leukocytes (WBCs) 3rd line: Immune system specific, acquired immunity “elite trained units” lymphocytes & antibodies
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AP Biology 2005-2006 2nd: Internal, broad range patrol leukocytes innate defense rapid response cells & proteins attack invaders that penetrate body’s outer barriers leukocytes phagocytic white blood cells anti-microbial proteins inflammatory response natural killer cells
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AP Biology 2005-2006 Leukocytes: Phagocytic WBCs Neutrophils attracted by chemical signals released by damaged cells enter infected tissue, engulf & ingest microbes amoeba-like (fierce!) lysosomes ~3 day life span Macrophages “big eater” bigger, long-lived phagocytes
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AP Biology 2005-2006 Lymph system Production & transport of leukocytes Traps foreign invaders lymph node lymph vessels (intertwined amongst blood vessels)
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AP Biology 2005-2006 Inflammatory response Damage to tissue triggers local inflammatory response histamines & prostaglandins released capillaries dilate, more permeable lead to clot formation increased blood supply swelling, redness & heat of inflammation & infection delivers WBC, RBC, platelets, clotting factors
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AP Biology 2005-2006 Fever When a local response is not enough systemic response to infection activated macrophages release interleukin-1 triggers hypothalamus in brain to readjust body thermostat to raise body temperature higher temperature helps defense inhibits bacterial growth stimulates phagocytosis speeds up repair of tissues causes liver & spleen to store iron reducing blood iron levels bacteria need large amounts of iron to grow
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AP Biology 2005-2006 3rd: Acquired Immunity Specific defense lymphocytes B lymphocytes (B cells) T lymphocytes (T cells) antibodies immunoglobulins Responds to… specific microorganisms specific toxins abnormal body cells antigens
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AP Biology 2005-2006 “self”“foreign” Antigens Proteins that serve as cellular name tags foreign antigens cause response from WBCs proteins belonging: viruses, bacteria, protozoa, parasitic worms, fungi, toxins non-pathogens: pollen & transplanted tissue B cells & T cells respond to different antigens B cells recognize intact antigens invaders in blood & lymph T cells recognize antigen fragments invaders which have infected cells
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AP Biology 2005-2006 Lymphocytes B cells mature in bone marrow humoral response system “humors” = body fluids produce antibodies T cells mature in thymus cellular response system Learn to distinguish “self” from “non-self” antigens during maturation
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AP Biology 2005-2006 Antibodies Proteins that bind to a specific antigen multi-chain proteins produced by B cells antibodies match molecular shape of antigens immune system has antibodies to respond to millions of antigens (invaders) tagging system “this is foreign!” each B cell has ~100,000 antigen receptors Y Y Y Y Y Y Y Y variable binding region Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
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AP Biology 2005-2006 How antibodies work
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AP Biology 2005-2006 B cell immune response tested by B cells 10 to 17 days for full response invader (foreign antigen) B cells + antibodies Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y recognition Y Y Y Y Y Y Y Y clone 1000s of clone cells Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y plasma cells release antibodies Y Y Y Y Y Y Y Y Y Y Y Y Y memory cells “reserves” Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y YY Y Y captured invaders
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AP Biology 2005-2006 1° vs 2° response to disease Memory B cells allow a rapid, amplified response with future exposure to pathogen
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AP Biology 2005-2006 How can we have so many antibody proteins & so few genes? Light chain Constant region Transcription of gene mRNA Chromosome of undifferentiated B cell B cell C C D J DNA of differentiated B cell Rearrangement of DNA V Translation of mRNA Antibody 40 genes for Variable region Variable region Heavy chain Variable DNA combinations: 1M different B cells 10M different T cells
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AP Biology 2005-2006 Vaccinations Active immunity immune system exposed to harmless version of pathogen Stimulates immune system to produce antibodies to invader rapid response if future exposure Most successful against viral diseases
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AP Biology 2005-2006 Passive immunity Maternal immunity antibodies pass from mother to baby across placenta or in breast milk critical role of breastfeeding in infant health mother is creating antibodies against pathogens baby is being exposed to Injection injection of antibodies short-term immunity
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AP Biology 2005-2006 How are cells tagged with antigens Glycoproteins on surface of cells have unique “fingerprint” major histocompatibility proteins (MHC) human leukocyte antigens (HLA) MHC proteins constantly export bits of cellular protein to cell surface “snapshot” of what is going on inside cell MHC proteins displaying self-antigens T cell
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AP Biology 2005-2006 How do T cells know a cell is infected Infected cells digest some pathogens & export pieces to MHC proteins on cell surface antigen presenting cells (APC) T cell MHC proteins displaying foreign antigens invading pathogen T cell antigen receptors
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AP Biology 2005-2006 T cell response helper T cell infected cell activated macrophage helper T cell stimulate B cells & antibodies Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y YY Y Y killer T cell activate killer T cells or interleukin 1 interleukin 2
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AP Biology 2005-2006 Attack of the Killer T cells Killer T cell binds to infected cell Destroys infected body cells binds to target cell secretes perforin protein punctures cell membrane of infected cell Infected cell destroyed Perforin punctures cell membrane Cell membrane Killer T cell Cell membrane Target cell Vesicle
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AP Biology 2005-2006 Immune response pathogen invasion antigen exposure free antigens in bloodantigens on infected cells humoral responsecellular response B cellsT cells macrophages helper T cells plasma B cells memory B cells memory T cells cytotoxic T cells Y Y Y Y YY Y Y antibodies Y Y Y
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AP Biology 2005-2006 HIV & AIDS Human Immunodeficiency Virus virus infects helper T cells helper T cells don’t activate rest of immune system: T cells & B cells also destroy T cells Acquired ImmunoDeficiency Syndrome infections by opportunistic diseases death usually from other infections pneumonia or cancer
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AP Biology 2005-2006 Immune system malfunctions Auto-immune diseases immune system attacks own molecules & cells lupus antibodies against many molecules released by normal breakdown of cells rheumatoid arthritis antibodies causing damage to cartilage & bone diabetes beta-islet cells of pancreas attacked & destroyed multiple sclerosis T cells attack myelin sheath of brain & spinal cord nerves Allergies over-reaction to environmental antigens allergens = proteins on pollen, from dust mites, in animal saliva
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