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65 Cards in this Set

  • Front
  • Back
pathogenicity
the ability of a microorganism to cause a disease
virulence
the degree of pathogenicity
LD50
number of microbes in a dose that will kill 50% of inoculated test animals (lethal dose 50%)
ID50
number of microbes in a dose required to cause an infection in 50% of population
adherence
enhances pathogenic potential, necessary step for most pathogens.
adhesins
molecules on the pathogen that bind to the host cell receptors
Capsules on pathogens
penetrate host defenses by resisting phagocytosis by leukocytes
leukocidins
enzyme that destroy neutrophils
hemolysins
enzyme that can lyse erythrocytes
coagulases
enzyme that can clot blood
kinases
enzyme that dissolve clots
hyaluronidase
enzyme that breaks down 'cell cement'
collagenase
enzyme that breaks down collagen in connective tissue
proteases
enzyme that breaks down proteins in muscle
lecithinase
enzyme that destroys plasma membranes
Antigenic variation
microbes alter their surface to evade immune system
Penetration into cytoskeleton
invasins rearrange actin filaments to propel pathogens into cell
Toxins
poisonous substances produced by some pathogens - most important substances of pathogenicity; exotoxins and endotoxins
Exotoxins
proteins produced inside pathogenic bacteria (most Gram +) then secreted into surrounding media following lysis
A-B Toxins
exotoxin - A (active) component is the enzyme. B (binding component) binds to host cell receptors and brings the enzyme into the cell
Membrane-disrupting toxins
(leukocidins, hemolysins) form channels in plasma membrane or disrupt phospholipid bilayer. this kills the cells
superantigens
proteins that provoke intense immune response; t-lymphocytes produce very high levels of cytokines that lead to fever, gi symptoms, shock and death
cytotoxins
kill host cells or affect their function
neurotoxins
interfere with nerve impulse transmission
enterotoxins
affect cells lining the gastrointestinal tract
Endotoxins
lipid portions of lipoplysaccharides (LPSs) that are part of the outer membrane of cell walls of gram- bacteria. these toxins are liberated when the cell dies and the wall breaks apart
septic shock (endotoxic shock)
shock caused by gram- bacteria. phagocytes ingest GNB produce "tumor necrosis factor" which damages capillaries, increases their permeability, causing large fluid loss and drop in BP
Pyrogenic response
(fever) to endotoxin caused by macrophage production if interleukin-1
Pathogen evasion of host defenses
grow inside cell, attachment sites mimic useful things to cells, attachment sites can also be hidden to immune system
Cytopatic effects (CPE)
visible effects of viral infection in cell culture: inclusion bodies, rounding, giant cell formation, cell death
Ciliary Escalator
Microbes in lowe rrespiraroy tract are trapped in mucus by goblet cells then propelled upward by cilia.
Plasma
liquid, non-cellular portion of blood
Serum
plasma without blood clotting proteins
phagocytosis
ingestion of microbe particles. Carried out mainly by neutrophils, eosinophils and macrophages
chemotaxis
chemical attraction o fphagocytes to mircoorganisms
adherence
attachment of phagocyte's plasma membrane to surface of microbe (enhanced by opsonization)
ingestion
pesudopods engulf microbe and form a phagosome
digestion
phagolysosome forms, digestive enzymes and bactericidal substances destroy microbe. residual body transports waste outside cell.
inflammation
destroys and removes injurious cells, walling off contamination, repairs damaged area.
interferons
antiviral proteins produced by animal cells to interfere with viral multiplication (not virus specific)
immunity
specific defensive responses to foreign organisms or other substances
Antigen (Ag)
substance that provokes a specific immune response
Antibody (Ab)
protein made in response to an antigen which can recognize and bind to that antigen (also called immunoglobulin (Ig)
epitope
specific region on an antigen that interacts with Antibody
Acquired immunity
specific resistance to infection developed during the life of the individual
Humoral / antibody-mediated immunity
involves production of antibodies by B lymphocytes
Cell-mediated immunity
involves specialized T lymphocytes that act against foreign cells
Hapten
molecule too small to stimulate Ab formation by itself, but can do so when attached to a larger carrier molecule
apoptosis
programmed cell death. Rids body of unneced cells, including B-Cells that do not find their specific antigen.
Helper T cell immunity
1. APC (dendritic cell) encouters/engulfs microorganism, breaksdown the antigen which combindes with MHC II molecules and are displayed on the surface of the sell
2.a receptor on the CD4+ T-helper cell binds to MHC II/antigen. CD4+ cell activates and produces cytokines
3. CD4+ cell proliferates and develops effector functions
Cell-Mediated cytotoxicity
1. CTL (cytotoxic t lymphocyte) detects abnormal cell endogeneous antigens
2. abnormal antigens are presented on the surface with MHC 1. CD8+T cells w receptors are transformed to CTLs
3. destruction of cell by apoptosis
How T-Cells active B cells to make antibody against t-dependent antigens
1. Ag is ingested by APC and partially digested. frags combinde with MHC and are presented on cell surface
2. Helper t cells specific for presented antigen interact with complex
3. helper cells activate an appropriate B cell. as well as antigen receptors
4. interaction triggers B cells to differentiate into plasma cell - secreting antibodies specific for the t-dependent antigen
vaccine
suspension of microorganism of fractions of microorganisms used to induce immunity
attenuated whole-agent vaccine
uses living but weakened microbes
inactivated whole-agent vaccine
uses killed microbes
toxoid
inactivated toxin that induces immunity response against toxin
subunit vaccine
antigentic fragments of a microbe that stimulates an immune response
conjugated vaccine
combination of antigens that enhance immune response
Nucleic Acid vaccine
naked microbe DNA injected, transcribed and translated into protien by the animal, immune response directed towards protein - experimental
adjuvant
substance that enhances effectiveness of antigens
titer
reciprocal of highest dilution given a positive result
Seroconversion
4-fold or greater increase in the titer between acute and convalescent phase = indicates infection
aggutination
rxn of particulate antigens with antibodies to form visible aggregates
direct agglutination
identify known bacteria types using known antibodies
Indirect Passive Agglutination
1. Rxn for Ab = particles coated with antigens / agglutination indicates presense of antibodies
2. rxn of particles covered by antigens and agglutination indicates presence of antibodies