talk twelve: the immune system chapter 20
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Biology Today (BIOL 109). Talk Twelve: The Immune System Chapter 20. The Immune System. Immunity is the ability to react to antigens so that the body remains free of disease. Disease is a state of homeostatic imbalance . Can be due to infection or failure of the immune system. - PowerPoint PPT PresentationTRANSCRIPT
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Talk Twelve:
The Immune System
Chapter 20
Biology Today (BIOL 109)
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The Immune System
• Immunity is the ability to react to antigens so that the body remains free of disease.– Disease is a state of homeostatic
imbalance.• Can be due to infection or failure of the
immune system.
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Primary Lymphatic Organs
• Lymphatic organs contain large numbers of lymphocytes (White Blood cells).
• Primary organs are:-– Red Bone Marrow.
• Site of stem cells.– Source of B
lymphocytes.
– Thymus Gland. Lymphocytes from bone marrow pass through to form T-lymphocytes
• Produces thymic hormones (thymosin).
• Aids in T lymphocyte maturation.
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Secondary Lymphatic Organs
• Secondary lymphatic organs are places where lymphocytes encounter and bind with antigens.– Spleen.– Lymph nodes.– Tonsils.– Peyer’s patches.
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Lymphatic Organs
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Secondary Lymphatic Organs
• Spleen – upper left of abdominal cavity behind stomach. Sectioned off by connective tissue- white pulp & red pulp.
– White pulp – lymphocytes
– Red pulp – filters blood. Blood entering the spleen passes through red pulp before it leaves (network of sinuses)
– FRAGILE
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Secondary Lymphatic Organs• Lymph Nodes – occur
along lymphatic vessels. Formed from connective tissue.– Packed full of B-
lymphocytes– As lymph courses
through sinuses it is filtered by macrophages, which engulf pathogens and debris.
– Also present- T-lymphocytes – fight infection and attack cancer cells
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Secondary Lymphatic Organs• Tonsils – patches of
lymphatic tissue. • Perform the same
function as lymph nodes– First line of defense
• Peyer’s Patches – on the intestinal wall and appendix. Attack pathogens that ender the body by way of the intestinal tract.
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Nonspecific Defenses• Barriers to Entry.
– Mucous membranes • Line respiratory, digestive, and urinary tract.
– Oil gland secretions.• Chemicals that kill or weaken bacteria on
skin
– Ciliated cells.• Sweep mucus & particles into throat
– Bacteria• Both in stomach and vagina, prevent
pathogens from gaining a foot-hold.
– Acid
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Innate Immunity• One important function of the immune system
is to promote growth and repair after injury– Either via physical damage or microorganisms
• The mobilization of innate immune cells to get rid of damaged cells or microorganisms is called inflammation
• Small molecules called cytokines are also involved
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Innate Immunity• Inflammatory Reaction.
– Tissue damage causes – tissue cells and mast cells to release chemical
mediators.
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Innate Immunity• Inflammatory Reaction.
•Histamine and kinins.– Capillaries dilate and become more permeable.
»Skin reddens and becomes warm.– Proteins and fluids escape from tissue.
Swelling occurs
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Innate Immunity• Inflammatory Reaction.
– Proteins and fluids escape from tissue and cause swelling.
»Swelling stimulates free nerve endings, causing the sensation of pain.
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Innate Immunity– Neutrophils and
Monocytes migrate to site of injury.
– Amoeboid – can change shape – squeeze through capillary walls and enter tissue fluid.
– Neutrophils engulf pathogens –destroyed by hydrolytic enzymes when fused to a lysosome
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Innate Immunity• Macrophages:
Monocytes change into these as they leave the blood and enter the tissues.– These are phagocytic
cells– Can eat many (100’s)
of pathogens and survive.
– Eat old blood cells and bits of dead tissue
– Stimulate the immune response.
• Increase production of white blood cells in bone marrow.
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Innate Immunity• Macrophages:
Monocytes change into these as they leave the blood and enter the tissues.
• Macrophages enter lymph vessels carring bacteria fragments to lymph nodes
• This starts a specific immune response
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Protective protein system• Known as Complement proteins
• Are activated when pathogens enter the body.• Complement certain immune responses.
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Protective protein system• Attract phagocytes.
• Form holes in bacteria.• Interferon binds to receptors of non-infected cells causing them to prepare for possible attack
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Specific immunity• Antigen--shape on cell, allows
recognition of self and detection of foreign cells.
• Antibody--protein that recognizes and binds antigens.
• Specific defenses respond to antigens.– Lymphocytes recognize an antigen due to
antigen receptors whose shape allows them to combine with a specific antigen.• Immunity is primarily the result of the action of B
lymphocytes and T lymphocytes.
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White blood cells•Granular Leukocytes
– Neutrophils: Most abundant. Have multilobed nucleus.•They are the first to respond to infection, and engulf
pathogens during phagocytosis.
– Eosinophils: Have bilobed nucleus•Known to increase in number in the event of
parasitic worm infection and during allergic reaction.
– Basophils: U-shaped or lobed nucleus.•In connective tissues release histamines along with Mast Cells
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White Blood Cells •Agranular Leukocyles
– Monocyles: Largest of the white blood cells.•Differentiate into even larger Macrophages•Phagocytize pathogens, old cells and debris•Stimulate production of other white blood cells
– Lymphocytes: Two types:•T-lymphocytes – Destroy any cell with foreign
antigens•B-lymphocytes – Produce antibodies that combine
with antigens
–Target pathogens for destruction
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Natural Killer Cells• Natural killer cells kill
virus-infected cells and tumor cells by cell-to-cell contact.– Large, granular
lymphocytes.
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T Cells
• Provide cell-mediated immunity.• Produced in bone marrow, mature in
thymus.• Antigen must be presented in groove of
HLA molecule.• Cytotoxic T cells destroy non-self
protein-bearing cells.• Helper T cells secrete cytokines that
control the immune response.
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B Cells• Provide antibody-mediated immunity
against bacteria.• Produced and mature in bone marrow.• Reside in spleen and lymph nodes.
– Circulate in blood and lymph.
• Directly recognize antigen and then undergo clonal selection.
• Clonal expansion produces antibody-secreting plasma cells and memory B cells.
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Clonal selection Theory• The antigen selects which
lymphocyte will undergo clonal expansion and produce more lymphocytes with the same type of antigen receptor.– Some become memory cells
– long term immunity to the same infection.
– B-cells become plasma cells – fight infection
– Apoptosis – when danger of infection is over, all plasma cells undergo programmed cell death
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Specific Defenses– Antibodies are
proteins shaped like an antigen receptor and capable of combining with, and neutralizing, a specific antigen.
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Antibodies• Classes.
– IgG - Enhances phagocytosis.– IgM - Activates complement proteins.– IgA - Prevents attachment of pathogens.– IgD - Antigen receptors on virgin B cells.– IgE - Immediate allergic response.
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Induced Immunity• Active Immunity.
– Immunization involves use of vaccines.
– Contain an antigen to which the immune system responds.
– Primary response. Secondary (booster) response.
– Dependent upon the presence of memory B and T cells capable of responding to lower antigen doses.
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Induced Immunity• Passive immunity
• occurs when an individual is given prepared antibodies.
– Temporary.•No memory
cells.•Primary and
secondary injections
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Issue - Allergies• Occurs when your immune system reacts
atypically to some antigens to which the host does not need protection.
• Pollen, dust mites, cats, a hard days work!– Called Allergens
• The atypical response produces a special antibody– IgE
• A form of innate immunity
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Allergies• IgE binds to mast cells.
• When a person later encounters the same allergen, the allergen binds to the IgE on the mast cell
• This triggers the explosive release of histamine
• Capillaries dilate and become more permeable.
• Skin reddens and becomes warm. Proteins and fluids escape from tissue. Swelling occurs
–
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Allergies• The large amounts of
histamines released in an allergic reaction cause strong symptoms
• Runny eyes, sneezing, or shortness of breath
• Depends upon the tissue in which the mast cells were triggered
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Allergies• As allergy symptoms are caused by histamines,
taking antihistamines stops the build up of histamines in the cells of blood vessels.
• However, antihistamines do not stop the immune response or the release of histamines in mast cells
• Other allergies are mediated by T-cells– Latex, poison ivy, dyes or chemicals in cosmetics or
clothing– Antihistamines do not help in these allergic
reactions
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Allergies• As each allergy is an antigen-specific immune
response it shows memory and a greater response on the next exposure– This is why allergies get worse over time
• Thousands of different substances can produce allergies in people – each triggered by a specific antigen-specific response– Why people are usually bothered by only a few
• Appears to be inherited– Remember human genetics and meiosis!!!!
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The End.
Any Questions?