MECHANISM OF INNATE IMMUNITY Flashcards
detection of PAMPs brings multiple components of immunity into play. what does it include?
the second line of defence:
CIPFIN
- complement system
- Inflammation
- phagocytes
- fever
- interferon
- NK cells action
what is the def of inflammation
The initial, rapid and localized response of the tissue due to damage/injury, infection, antigen challenge and physical/chemical damage or other trauma.
Acute inflammation plays role in innate immunity by:
i) Destroying the infectious agent and remove it and its by products and
any cell debris.
ii) Localize the infectious agents by building a ‘wall’ around them so that
they do not spread to neighbouring sites.
iii) Heal, repair, and replaced the damaged tissue.
uring inflammation process, damaged mast cells and leukocytes release chemicals, give two examples.
- histamines
- kinin
what is the sequence of events that occur in inflammation?
- vasodilation of the blood vessels - increase blood flow and bring loads of immune system cells
- increase permeability of the blood vessels - so some leukocytes, plasma and antibodies can leak out into the infected tissue. leuk will phagocytose invading pathogens.
- chemokines (mediators of inflammation) are induced in response to infection - act as chemoattractants, attract more leukocytes which cause extravasation process.
- systemic response may occur like fever which will help to accelerate the proliferation of leukocytes.
what are the common cardinal signs of acute inflammation?
- redness - due to increased blood flow
- hotness - due to increased metabolic activity
- swelling - due to leakage of fluid from capillaries
- painful - the process stimulate nerves and cause pain
- loss of function
what is the def of phagocytosis?
The process of ingestion of
solid substances (e.g. cells, bacteria,
parts of necrosed tissue) by phagocytes and transported to a site within the phagocytes where it is broken down by lysosomal enzymes.
what does the traumatized tissues produce when an infection begins?
chemokines.
what is the function of chemokines?
The presence of chemokines signals
phagocytes to move to the damaged site by chemotaxis.
Once some phagocytes reach the damaged site, they also release
chemokines, why?
to amplify the effectiveness of the defensive response.
what are the two most active phagocytes?
i) Neutrophils: engulf between 5 to 20 bacteria - become inactive and
die.
ii) Macrophages: engulf up to 100 bacteria, debris from damaged cells
and foreign matter.
how does phagocytosis work?
1) Chemotaxis: phagocytes are attracted to site of infection.
2) Microbe binds to receptors on phagocyte. Pseudopodia surround
microbe and engulf it.
3) The pathogen is now contained in phagosome @ phagocytic vesicle.
Phagosome moves deeper into cell.
4) A lysosome fuses with the phagosome – it forms phagolysosome.
5) Contents from lysosome digests the microbe within the phagolysosome.
6) Content of lysosome further digest the microbe, forming the residual body containing indigestible material.
7) Contents of phagolysosome is eliminated by exocytosis.
what is pus and how does it relates to phagocytosis?
- After a few days, the area is full of
dead cells, which form pus. - The contents of pus are dead
neutrophils, tissue debris and some
remaining pathogens. - The pus may break through the
surface of the skin or broken down and absorbed into the surrounding tissue.
how does the fever develop?
Some cytokines may function as endogenous pyrogen (e.g. interleukin 1), which induces the development of fever
it occurs especially when the invading organisms have spread into the blood.
what produced the exogenous pyrogen?
the invading pathogens. e.g. bacterial toxins
what does the both pyrogen cause?
Both pyrogens cause release of prostaglandin within hypothalamus – resets the hypothalamus temperature control thus resulting in elevation in body temperature
why is fever a beneficial responses?
i) it inactivates many bacterial toxins by changing their 3D shape.
ii) it lowers plasma iron concentration – without iron, pathogens do not
grow well.
iii) it increases the speed of host defenses process – augment
phagocytosis, increase the rate of many enzyme-dependent inflammatory activities & promotes production of immune cells.
iv) fever makes a person feel ill, thus forces a person to rest - allowing all
available energy to be used for fighting off infection.
but what if the body temp went too high?
i) vasoconstriction occur – inhibits the movement of phagocytes.
ii) rate of metabolism increased – making the heart work harder.
iii) denaturation of proteins occur.
iv) nerve impulses is inhibited.
v) electrolyte imbalance occur due to loss of water.
what are the effects of things that occur when body temp is too high?
hallucinations, convulsions, coma and death.
what is complement system?
a group of soluble proteins and glycoproteins, many of which exist in inactive forms.
how can it be activated?
i) Alternate complement pathway: binding directly to a foreign invader
nonspecifically activates the complement cascade (innate immune
response).
ii) Classical complement pathway: binding to antibodies produced against and attached to a particular foreign invader specifically activates the complement cascade (adaptive immune response).
when complement becomes attached, or fixed, to foreign substances,______
it is activated and becomes a major factor in the fight against foreign substances.
The complement fixation mediates_______.
opsonization, activation of
inflammation and formation of membrane attack complexes that causes cell lysis
what is interferon and how does it work?
viruses enter the host cell as part of the infectious process.
When cells are infected with viruses, they produce interferons.
Interferon is a protein produced by virus-infected host cells and released
from those cells.
Interferon then diffuses to the surrounding uninfected cells and prompts them to make antiviral proteins.
Antiviral proteins degrade viral mRNA, stop viral replication and also
inhibit protein synthesis.
is interferons virus specific?
Interferons are not virus-specific – are produced in response to any viral
infection.
what does interferons do besides facilitating inhibition of viral replication?
i) enhances phagocytic activity of macrophages.
ii) stimulates production of antibodies
iii) boosts the power of killer cells.
iv) slows cell division and suppresses tumor growth.
what is NK cells?
NK cells is natural killer cells that are involved in the innate immune response in two ways,
- target cell killing
- production of cytokines.
what does NK cells release?
i) perforin (and other molecules) which form pores in the cell membrane of the target cell.
ii) granzymes which induce apoptosis or cell lysis.
NK cells destroy cells infected by_______.
virus and tumor cells.
