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Micro: Chapter 16
Microbiology chapter 16 for Indiana State University
34
Microbiology
Undergraduate 2
11/04/2013

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Term
Susceptibility
Definition
  • Lack of resistance to a disease
Term
Immunity
Definition
  • Ability to ward off disease
Term
Innate Immunity
Definition
  • defenses against any pathogen
Term
Adaptive Immunity
Definition
  • immunity or resistance to a specific pathogen
Term
First line of defense
Definition
  • Intact skin
  • Mucous membranes and their secretions
  • Normal microbiota
Term
Second line of defense
Definition
  • Phagocytes, such as neutrophils, eosinophils, dendritic cells, and macrophages
  • Inflammation
  • Fever
  • Antimicrobial substances
Term
Third line of defense
Definition
  • Specialized lymphocytes: T cells and B cells
  • Antibodies
Term
The Concept of Immunity
Definition
  • Host Toll-like resceptors (TLRs) attach to pathogen-associated molecular patterns (PAMPs)- rectptors on human cells that recognize various common bacterial substances such as peptidoglycan
  • TLRs induce cytokines that regulate the intensity and duration of immune responses
Term
Physical Factors
Definition
  • Skin
  • Epidermis consists of tightly packed cells with 
    • Keratin, a protective protein
  • Mucous membranes
  • Mucus: traps microbes
  • Ciliary escalator: transports microbes trapped in mucus away from the lungs
  • Lacrimal apparatus: washes eye
  • Saliva: washes microbes off
  • Urine: flows out
  • Vaginal secretions: flow out
Term
Chemical factors
Definition
  • 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
Term
Normal microbiota
Definition
  • Microbial antagonism/competitive exclusion: normal microbiota compete with pathogens or alter the environment
  • Commensal micrbiota: one organism (microbe) benefits, and the other (host) is unharmed
    • May be opportunistic pathogens
Term
Types of Leukocytes
Definition
  • Granulocytes
    • Neutrophils
    • Basophils
    • Eisinophils
  • Agranulocytes
    • Monocytes
    • Dendritic cells
    • Lymphocytes
    • T cells
    • B cells
Term
Phagocytosis
Definition
  • Phago: from Greek, meaning eat
  • Cyte: from Greek, meaning cell
  • Ingestion of microbes or particles by a cell performed by phagocytes
Term
Oxidative Burst
Definition
  • Bacterium adheres to membrane of neutrophil
  • NADPH is produced
  • NADPH oxidase uses electron from NADPH to produce superoxide
  • Superoxide dismutase converts superoxide to hydrogen peroxide 
  • Hydrogen peroxide burst kills bacterium
Term
Microbial Evasion of Phagocytosis
Definition
  • Inhibit adherence: M proten, capsules- Streptococcus pyogenes, S. pneumoniae
  • Kill phagocytes: leukocidins- Staphlyococcus aureus
  • Lyse phagocytes: membran attack complex- Listeria monocytogenes
  • Escape phagosome- Shigella, Rickettsia
  • Prevent phagosome-lysosome fusion- HIV, Mycobacterium tuberculosis
  • Survive in phagolysosome- Coxiella burnettii
Term
Inflammation
Definition
  • Activation of acute-phase proteins (complement, cytokine, and kinins)
  • Vasodilation (histamine, kinins, prostaglandins, and leukotrienes) 
  • Redness
  • Swelling (edema)
  • Pain
  • Heat
Term
Histamine
Definition
  • Vasodilation, increased permeability of blood vessels
Term
Kinins
Definition
  • Vasodilation, increased permeability of blood vessels
Term
Prostaglandins
Definition
  • Intensify histamine and kinin effect
Term
Leukotrienes
Definition
  • Increased permeability of blood vessels, phagocytic attachment
Term
Process of inflammation
Definition
  1. Chemicals such as histamine, kinins, prostaglandins, leukotrienes, and cytokines are released by damaged cells
  2. Blood clot forms
  3. Abscess starts to form
  4. Margination- phagocytes stick to endothelium
  5. Diapedesis- Phagocytes squeeze between endothelial cells
  6. Phagocytosis of invading bacteria occurs
Term
Fever
Definition
  • Abnormally high body temperature
  • Hypothalamus is normall set at 37C
  • Gram-negative endotoxins cause phagocytes to release interleukin-1 (IL-1)
  • Hypothalamus releases prostaglandins that reset the hypothalamus to a high temperature
  • Body increases rate of metabolism, and shivering occurs, which raise temperature 
  • Vasodilatin and sweating: body temperature falls (crisis)
Term
Advantages/Disadvantages
Definition
  • Advantages
    • Increases transferrins
    • Increases IL-1 activity
    • Produces interferon
  • Disadvantages
    • Tachycardia
    • Acidosis
    • Dehydration
    • 44-46o C fatal
Term
The complement system
Definition
  • Serum proteins activated in a cascade
  • Activated by 
    • Antigen-antibody reaction
    • Proteins C3 and a pathogen
  • C3b causes opsonization
  • C3a+ C5a cause inflammation
  • C5b+ C6 + C7 + C8 + C9 cause cell lysis
Term
Outcomes of complement activation
Definition
  1. Inactivated C3 splits into activated C3a and C3b
  2. C3b binds to microbe, resulting in opsonization
  3. C3b also splits C5 into C5a and C5b
  4. C5b, C6, C7, and C8 bind together sequentially and insert into the microbial plasma membrane, where they function as a recptor to attract a C9 fragments are added to form a channel. Together, C5b through C8 and the multiple C9 fragments form the membrane attack complex, resulting in cytolysis. 
  5. C3a and C5a cause mast cells to release histamine, resulting in inflammation; C5a also attracts phagocytosis
Term
Effects of Complement Activation
Definition
  • Opsonization: enhanced phagocytosis
  • Membrane attack complex: lysis of the invader
  • Attract phagocytes by chemotaxis
Term
Classical pathway of complement activation
Definition
  • C1 is activated by binding to antigen-antibody complexes
  • Activated C1 splits C2 into C2a and C2b, and C4 into C4a and C4b
  • C2a and C4b combine and activate C3, splitting it into C3a and C3b
Term
Some bacteria evade complement
Definition
  • Capsules prevent C activation
  • Surface lipid-carbohydrate complexes prevent formation of membrane attack complex (MAC)
  • Enzymatic digestion of C5a
Term
Interferons
Definition
  • IFN-alpha and IFN-beta: cause cells to produce antivirla proteins that inhibit viral replication
  • IFN-gamma: causes neutrophils and macrophages to phagocytize bacteria
Term
Antiviral action of alpha and beta interferons
Definition
  1. Viral RNA from an infecting virus enters the cells
  2. The infecting virus replicated into new viruses
  3. The infecting virus also induces the host dcell to produce interferon mRNA (IFN-mRNA), which is translated into alpha and beta interferons.
  4. Interferons released by the virus-infected host cell bind to plasma membrane or nuclear membrane receptors on unlimited neighboring host cells, inducing them to synthesize antiviral proteins (AVPs). These include oligoadenylate synthetase and protein kinase.
  5. New viruses released by the virus-infected host cell infect neighboring host cells
  6. AVP's degrade viral mRNA and inhibit protein synthesis - and thus interfere with viral replication. 
Term
Transferrins
Definition
  • Bind serum ion
Term
Antimocrobial peptides
Definition
  • Lyse bacterial cells
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