yet again another pandemic threat
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Yet Again another Pandemic threat. http://www.who.int/csr/disease/avian_influenza/phase/en/index.html. - PowerPoint PPT PresentationTRANSCRIPT
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Yet Again another Pandemic threat
http://www.who.int/csr/disease/avian_influenza/phase/en/index.html
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• An influenza pandemic occurs when a new influenza virus appears against which the human population has no immunity, resulting in epidemics worldwide with enormous numbers of deaths and illness.
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• Outbreaks of influenza in animals, especially when happening simultaneously with annual outbreaks of seasonal influenza in humans, increase the chances of a pandemic, through the merging of animal and human influenza viruses.
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• During the last few years, the world has faced several threats with pandemic potential, making the occurrence of the next pandemic a matter of time.
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Some Links
• Timeline for vaccine• A fact sheet on swine flue• who Now list this a N1H1 post pandemic p
eriod, N1H1 becomes pare of our seasional flue
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Some Numbers
• Many Millions get flue• Each year 200,000 hospitalized• 35,000 die
• Mortality rate 0.1%• SARS 10%• Bird flue up to 90%• Swine flue? Is it really 10%?
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Nonspecific Immunity
Resistance don’t get itSusceptibility get it
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• Nonspecific immunity (innate immunity) are the defenses that protect the body against any pathogen.– Are not normally set up against any particular
pathogen.• Adaptive immunity: Immunity, resistance
to a specific pathogen
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An Overview of the Body’s Defenses
Figure 16.1
ANIMATION Host Defenses: The Big Picture
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The Concept of Immunity
• Host Toll-like receptors (TLRs) attach to Pathogen-associated molecular patterns (PAMPs)
• TLRs induce cytokines that regulate the intensity and duration of immune responses
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The skin• Mechanical
– Skin Structure– Saliva washes– Mucus traps and ciliary escalator– Urine, vaginal flows out
• Chemical– Sebum w/ unsaturated fatty acids– Perspiration– Lysozyme– Acid conditions stomak(1.2-3pH) skin (3-5pH)– Normal microbiota– Transferrins, and NO
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Physical Factors
• Skin• Epidermis
consists of tightly packed cells with– Keratin, a
protective protein
Figure 16.2
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Ciliary Escalator
Figure 24.7
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Ciliary Escalator
Figure 16.4
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Phagocytosis
• Define.• What does this look like?• What does this do?
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Chemical Factors
• Fungistatic fatty acid in sebum• Low pH (3–5) of skin• Lysozyme in perspiration, tears, saliva, and
urine• Low pH (1.2–3.0) of gastric juice• Low pH (3–5) of vaginal secretions
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Normal Microbiota and Innate Immunity
• Microbial antagonism/competitive exclusion: Normal microbiota compete with pathogens or alter the environment
• Commensal microbiota: One organism (microbe) benefits and the other (host) is unharmed– May be opportunistic pathogens
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Red Blood Cells Transport O2 and CO2
White Blood Cells:Neutrophils Phagocytosis
Basophiles Histamine
Eosinophils Kill parasites
Formed Elements in Blood
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Formed Elements in Blood
Monocytes Phagocytosis
Dendritic cells Phagocytosis
Natural killer cells Destroy target cells
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Formed Elements in Blood
T cells Cell-mediated immunity
B cells Produce antibodies
Platelets Blood clotting
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• Percentage of each type of white cell in a sample of 100 white blood cells
Neutrophils 60–70%
Basophils 0.5–1%
Eosinophils 2–4%
Monocytes 3–8%
Lymphocytes 20–25%
Differential White Cell Count
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• Neutrophils: Phagocytic• Basophils: Produce histamine• Eosinophils: Toxic to parasites, some
phagocytosis• Monocytes: Phagocytic as mature
macrophages• Fixed macrophages in lungs, liver, bronchi• Wandering macrophages roam tissues• Lymphocytes: Involved in specific immunity
White Blood Cells
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Components of Lymphatic System
Figure 16.5a
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The Lymphatic System
Figure 16.5b–c
ANIMATION Host Defenses: Overview
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Phagocytosis
• Phago: From Greek, meaning eat
• Cyte: From Greek, meaning cell
• Ingestion of microbes or particles by a cell, performed by phagocytes
Figure 16.6
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Figure 16.7
Phagocytosis
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Phagocytosis
ANIMATION Phagocytosis: Mechanism
ANIMATION Phagocytosis: Overview
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Inhibit adherence: M protein, capsules
Streptococcus pyogenes, S. pneumoniae
Kill phagocytes: Leukocidins
Staphylococcus aureus
Lyse phagocytes: Membrane attack complex
Listeria monocytogenes
Escape phagosome Shigella, Rickettsia
Prevent phagosome-lysosome fusion
HIV, Mycobacterium tuberculosis
Survive in phagolysosome
Coxiella burnettii
Microbial Evasion of Phagocytosis
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Actions of phagocytic cells
• Neutrophils (granulocyte) phagocyte• Increase in number during infection
(leukocytosis)• Neutrophils are most important• Can act as antigen presenting cells (APC)
– Important in specific resistance
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Mechanism of phagocytosis
• Chemotaxis to pathogen• Adherence• Engulfment• Killing
• Resistance of microbes can be seen in some ability to live even after phagocytosis.
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• Redness• Pain• Heat• Swelling (edema)• Acute-phase proteins activated (complement,
cytokine, kinins)• Vasodilation (histamine, kinins,
prostaglandins, leukotrienes)• Margination and emigration of WBCs• Tissue repair
Inflammation
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Chemicals Released by Damaged Cells
• Histamine Vasodilation, increased permeability of blood vessels
• Kinins Vasodilation, increased permeability of blood vessels
• Prostaglandins Intensity histamine and kinin effect
• Leukotrienes Increased permeability of blood vessels, phagocytic attachment
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Fever
• Body temp is controlled by the brain• High temp in response to IL-1• Caused by
– Bacterial endotoxins– Interleukin-1– Chills indicate rising body temp (crisis)
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Fever
• Advantages– Increases
transferrins– Increases IL–1
activity– Produces Interferon
• Disadvantages– Tachycardia– Acidosis– Dehydration– 44–46°C fatal
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Antimicrobial substances
• IFN- and IFN-: Cause cells to produce antiviral proteins that inhibit viral replication
• Gamma IFN: Causes neutrophils and macrophages to phagocytize bacteria
• Lysozyme• Acids on skin• Complement
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Antiviral Actions of Interferons (IFNs)
Figure 16.15
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Innate Immunity
• Transferrins– Bind serum iron • Antimicrobial
peptides– Lyse bacterial cells
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• Deficiencies in complement can result in an increased susceptibility to disease
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The Complement System
• Serum proteins activated in a cascade• Activated by
– Antigen-antibody reaction– Proteins C3, B, D, P and a pathogen
ANIMATION Complement System: Activation
ANIMATION Complement System: Overview
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The Complement System
• C3b causes opsonization• C3a + C5a cause inflammation• C5b + C6 + C7 + C8 + C9 cause cell lysis
ANIMATION Complement System: Results
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The Complement System
Figure 16.9
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Effects of Complement Activation• Opsonization or immune adherence:
Enhanced phagocytosis• Membrane attack complex: Cytolysis• Attract phagocytes
Figure 16.10
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Inflammation Stimulated by Complement
Figure 16.11
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Classical Pathway of Complement Activation
Figure 16.12
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Alternative Pathway of Complement Activation
Figure 16.13
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Lectin Pathway of Complement Activation
Figure 16.14
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Some Bacteria Evade Complement
• Capsules prevent C activation• Surface lipid-carbohydrates prevent
membrane attack complex (MAC) formation• Enzymatic digestion of C5a