Micro Test 2

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