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Specificity
-that an immune response able to contain one microbial pathogen is rarely effective against a second microbe
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Universality
The immune system can attack virtually all microbes. Using different more specific tools.
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Inducibility
- -immune responses take time (several days to several weeks) to develop
- - defenses are not usually present at the time of first infection.
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innate resistance
- -non-immune defense mechanisms
- -Innate defense mechanisms are constitutive whereas immune responses are inducible.
- ex:skin, innate defenses by cells and molecules in blood.
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Four main processes of innate defense
- Inflammation
- Phagocytosis
- Processes initiated by complement
- Interferon production
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Inflammation
-when skin is breached and signals are given for blood vessels to release blood cells and fluid containing multiple forms of defense near the site.
ex- histamine stored in mast cells
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Phagocytosis
- -when cells present in blood ingest foreign particles first by binding, enveloping and then digestion.
- -effective against bacteria
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Macrophages
- -What Neutriphils and monocytes are called when they leave blood and enter tissue
- -Phagocytic cells
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6 steps of phagocytosis
for phagocytes
- 1 activation
- 2 Chemotaxis
- 3 recognition and adherence
- 4 ingestion
- 5 digestion and killing
- 6 expulsion
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1 activation in phagocytosis
When a resting neutriphil is activated my inflammatory mediators
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2 Chemotaxis in phagocytosis
when an activated neutrophil follows trail of chemotactic mediators to site of infection
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3 recognition and adherence in phagocytosis
-oposonin linking molecules biuld bridge between phagocyte and bacterium.
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Phagocytes may not be able to adhere if bacterium has ___ or ___ ___
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4 ingestion in phagocytosis
- -pseudopods extend from neutrophil to surround bacterium
- -when pseudopods meet a phagosome is formed around bacterium
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5 killing and digestion in phagocytosis
-Phagosome fuses with a Lysosome to create a Phagolysosome where bacterium is killed and then digested
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6 expulsion in phagocytosis
-phagolysosome fuses with cell membrane to expel undigestable parts of bacterium
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Processes initiated by complement
Complement consists of a series of interacting proteins moving away from infection to activate downstream proteins to aid in fighting the infection
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How are dormant downstream proteins activated in compliment?
cleavage by proteolysis
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The classical pathway occurs as part of ___ responses
- immune
- -discovered before alternative but is of more recent origin in evolution.
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alternative pathway, is involved in ___ defense.
innate
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three distinct processes of innate resistance Complement is involved in
- (i) Complement components are involved as inflammatory mediators (complement cascade)
- (ii) An activated component of the third component of complement, C3, called C3b, binds to the surface of many bacteria and aids the process of phagocytosis by such cells as macrophages.
- (iii) Binding of C3b to the surface of a bacterial cell initiates a series of molecular events that leads to the formation of the membrane attack complex
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membrane attack complex
formed by binding of C3b to bacteria resulting in the formation of holes in membranes, and subsequent lysis (death due to leaking) of the bacterium.
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Interferon(IFN)
-an important defense against viral infections, -interferes with viral replication
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three kinds of interferon
a and b interferon production occurs in cells infected by viruses.
IFN-a produced by infected Lymphocytes
IFN-B produced by infected fibroblasts (a type of connective tissue cell)
IFN-y -signal other cells to produce antiviral proteins (avp) that interfere with viral protein synth. activates macrophages
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immunization
-The establishment of resistance to a pathogen by administering an attenuated form of the microorganism.
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Attenuation examples
-chicken cholera
-anthrax bacillus
-prolonged culture of chicken cholera under anaerobic conditions (absence of oxygen)
- - Culture of the anthrax bacillus at 42C as opposed to 37C
- -passage through other animal species could lower the virulence
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it was first thought that immunization was only for ___ ___ but it can be achieved against virtually any ___ ___
- virulent organisms
- foreign substance
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Sabin vaccine
attenuated virus
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exotoxin
a poison shed/excreted by a pathogen
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toxoid
a toxin treated in such a way (e.g. by heating it) that it is no longer toxic
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serum
cell-free yellow liquid that separates from the red sticky mass of clumped cells and inactivates toxins
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passive transfer of immunity
administration of serum from immune animals to normal, unimmunized animals confers protection against specific toxins
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antibodies
-protective molecules present in immune serum that bind to an antigen and call upon various mechanisms to attack it
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antigens
- -The molecules or substances to which antibodies specifically bind
- -located on:toxins, pathegens, allergens
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agglutination
when antigen bearing molecules (toxins, bacterial, allergens) are bound together by antibodies and precipitated
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PRECIPITIN REACTION
the reaction between an antibody and its specific soluble antigen that results in precipitation of the antigen
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In vitro demonstration of compliment-Heated
immune serum provides the highly specific antibodies and kills everything else - normal serum provides the heat susceptible non-specific complement required to obtain lysis of the bacteria
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three examples of how antibodies add specificity to the mechanisms of innate resistance by acting as an adaptor or connector(3)
- 1 Activation of complement
- 2 Enhancement of phagocytosis
- 3 Triggering acute inflammation
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Activation of complement by antibodies
when antibodies bind a cell it activates compliment
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Enhancement of phagocytosis by antibodies
after antibodies bind to the surface of a specific bacterium, macrophages bind to them with surface receptors allowing envelopment to occur.
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opsinins
- -molecules that enhance phagocytosis by bonding to both bacterium and phagocyte
- ex:antibodies(IgG, IgM), C3b
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Triggering of acute inflammation by antibodies
if a cytophilic antibody(IgE) is bonded to a mast cell when it interacts with an antigen the mast cell is forced to discharge its granules which contain histamine causing inflammation
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