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-that an immune response able to contain one microbial pathogen is rarely effective against a second microbe
The immune system can attack virtually all microbes. Using different more specific tools.
- -immune responses take time (several days to several weeks) to develop
- - defenses are not usually present at the time of first infection.
- -non-immune defense mechanisms
- -Innate defense mechanisms are constitutive whereas immune responses are inducible.
- ex:skin, innate defenses by cells and molecules in blood.
Four main processes of innate defense
- Processes initiated by complement
- Interferon production
-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
- -when cells present in blood ingest foreign particles first by binding, enveloping and then digestion.
- -effective against bacteria
- -What Neutriphils and monocytes are called when they leave blood and enter tissue
- -Phagocytic cells
6 steps of phagocytosis
- 1 activation
- 2 Chemotaxis
- 3 recognition and adherence
- 4 ingestion
- 5 digestion and killing
- 6 expulsion
1 activation in phagocytosis
When a resting neutriphil is activated my inflammatory mediators
2 Chemotaxis in phagocytosis
when an activated neutrophil follows trail of chemotactic mediators to site of infection
3 recognition and adherence in phagocytosis
-oposonin linking molecules biuld bridge between phagocyte and bacterium.
Phagocytes may not be able to adhere if bacterium has ___ or ___ ___
4 ingestion in phagocytosis
- -pseudopods extend from neutrophil to surround bacterium
- -when pseudopods meet a phagosome is formed around bacterium
5 killing and digestion in phagocytosis
-Phagosome fuses with a Lysosome to create a Phagolysosome where bacterium is killed and then digested
6 expulsion in phagocytosis
-phagolysosome fuses with cell membrane to expel undigestable parts of bacterium
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
How are dormant downstream proteins activated in compliment?
cleavage by proteolysis
The classical pathway occurs as part of ___ responses
- -discovered before alternative but is of more recent origin in evolution.
alternative pathway, is involved in ___ defense.
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
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.
-an important defense against viral infections, -interferes with viral replication
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
-The establishment of resistance to a pathogen by administering an attenuated form of the microorganism.
-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
it was first thought that immunization was only for ___ ___ but it can be achieved against virtually any ___ ___
- virulent organisms
- foreign substance
a poison shed/excreted by a pathogen
a toxin treated in such a way (e.g. by heating it) that it is no longer toxic
cell-free yellow liquid that separates from the red sticky mass of clumped cells and inactivates toxins
passive transfer of immunity
administration of serum from immune animals to normal, unimmunized animals confers protection against specific toxins
-protective molecules present in immune serum that bind to an antigen and call upon various mechanisms to attack it
- -The molecules or substances to which antibodies specifically bind
- -located on:toxins, pathegens, allergens
when antigen bearing molecules (toxins, bacterial, allergens) are bound together by antibodies and precipitated
the reaction between an antibody and its specific soluble antigen that results in precipitation of the antigen
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
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
Activation of complement by antibodies
when antibodies bind a cell it activates compliment
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.
- -molecules that enhance phagocytosis by bonding to both bacterium and phagocyte
- ex:antibodies(IgG, IgM), C3b
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