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
Yet Again another Pandemic threat
http://www.who.int/csr/disease/avian_influenza/phase/en/index.html
• 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.
• 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.
• 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.
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
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%?
Nonspecific Immunity
Resistance don’t get itSusceptibility get it
• 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
An Overview of the Body’s Defenses
Figure 16.1
ANIMATION Host Defenses: The Big Picture
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
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
Physical Factors
• Skin• Epidermis
consists of tightly packed cells with– Keratin, a
protective protein
Figure 16.2
Ciliary Escalator
Figure 24.7
Ciliary Escalator
Figure 16.4
Phagocytosis
• Define.• What does this look like?• What does this do?
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
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
Red Blood Cells Transport O2 and CO2
White Blood Cells:Neutrophils Phagocytosis
Basophiles Histamine
Eosinophils Kill parasites
Formed Elements in Blood
Formed Elements in Blood
Monocytes Phagocytosis
Dendritic cells Phagocytosis
Natural killer cells Destroy target cells
Formed Elements in Blood
T cells Cell-mediated immunity
B cells Produce antibodies
Platelets Blood clotting
• 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
• 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
Components of Lymphatic System
Figure 16.5a
The Lymphatic System
Figure 16.5b–c
ANIMATION Host Defenses: Overview
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
Figure 16.7
Phagocytosis
Phagocytosis
ANIMATION Phagocytosis: Mechanism
ANIMATION Phagocytosis: Overview
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
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
Mechanism of phagocytosis
• Chemotaxis to pathogen• Adherence• Engulfment• Killing
• Resistance of microbes can be seen in some ability to live even after phagocytosis.
• 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
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
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)
Fever
• Advantages– Increases
transferrins– Increases IL–1
activity– Produces Interferon
• Disadvantages– Tachycardia– Acidosis– Dehydration– 44–46°C fatal
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
Antiviral Actions of Interferons (IFNs)
Figure 16.15
Innate Immunity
• Transferrins– Bind serum iron • Antimicrobial
peptides– Lyse bacterial cells
• Deficiencies in complement can result in an increased susceptibility to disease
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
The Complement System
• C3b causes opsonization• C3a + C5a cause inflammation• C5b + C6 + C7 + C8 + C9 cause cell lysis
ANIMATION Complement System: Results
The Complement System
Figure 16.9
Effects of Complement Activation• Opsonization or immune adherence:
Enhanced phagocytosis• Membrane attack complex: Cytolysis• Attract phagocytes
Figure 16.10
Inflammation Stimulated by Complement
Figure 16.11
Classical Pathway of Complement Activation
Figure 16.12
Alternative Pathway of Complement Activation
Figure 16.13
Lectin Pathway of Complement Activation
Figure 16.14
Some Bacteria Evade Complement
• Capsules prevent C activation• Surface lipid-carbohydrates prevent
membrane attack complex (MAC) formation• Enzymatic digestion of C5a