Immunology 1: Immune system & its Defence mechanisms Flashcards
The immune system provides defence against?
microbial pathogens & cancer
Three characteristics of immune responses?
Specificity, universality & adaptability
What does specificity encompass?
Immune response that’s able to contain one microbial pathogen isn’t effective against 2nd microbe unless the 2 are closely related
What does universality encompass?
- immune system can respond to whole universe of foreign substances
- immune system can attack virtually all microbes
What does adaptability refer to?
- immune responses take time to develop (1-2 weeks)
- defences provides by response not present at time of first infection
Primary & secondary immune responses?
- primary follows primary infection
- 2ndary follows 2ndary infection
- 2ndary response faster & more intense than 1st (why vaccinations work)
2ndary response example of?
positive memory
Negative memory example?
pre-exposure to antigen results in lessened ability to respond to subsequent challenge of antigen
immune systems first seen in?
lower vertebrate animals
-newer evolutionary trait
innate resistance?
- invertebrates & vertebrates have this (only vertebrates have immune system)
- non-immune defence systems
- evolved before immune system did
- mechanisms often effective at time of infection & characteristics change little following infection
Innate defence mechanisms are ___ where as immune responses are ____.
constitutive; inducible (form of adaptability)
3 defence systems of a vertebrate?
1 - surface of body (skin, chemical/physical barrier)
2 - innate defences by cells & molecules in blood (provide protection if 1st barrier fails)
3 - immune system comes into play if first 2 fail
3 characteristics of innate defence?
- immediate protection
- non specific
- constitutive or uninductible
4 processes of innate defence?
inflammation, phagocytosis, processes initiated by compliment, interferon production.
Acute inflammation (innate defence process)
if you scratch (damage) skin, red line will appear & within minutes will have broadened/swelled.
- many forms of defence are brought to site when first barrier of protection is damaged
- signals given to blood cells (mast cells) & fluid to escape blood vessels in injury vicinity
Role of histidine in acute inflammation?
- stored in mast cells
- released at site of injury causing local inflammation in area!
- central role in initiating inflammatory response
Phagocytosis (innate defence process)
- phago = I eat
- important in having protection against bacteria
- bind bacteria to phagocytic cell surface (phagosome)
- phagosome fuses w lysosome (phagolysosome) where enzymes attack & ‘digest’ bacterium
- neutrophils & monocytes most important ones: macrophages -> enter tissues from blood
Processes initiated by complement (innate defence process)
- complement earlier in evolution than immune systems
- series of interacting proteins
- one protein component activates many others ‘downstream’ from it causing its cleavage by proteolysis = complement cascade
complement cascade initiation?
- classical: discovered first, more evolutionarily recent. Part of immune response
- alternative: part of innate defence
How are complement components involved in innate defence?
- inflammatory mediators (activate neutrophils)
- activated component of C3 called C3b (binds to bacteria, aids in phagocytosis)
- binding of C3b to bacteria leads to formation of membrane attack complex (makes holes in memb & lysis of bacteria - death bc of leaking)
What happens if a phagocyte cannot adhere to bacterium?
linking molecules (opsonins) facilitate by building bridge b/n phagocyte & bacteria
Steps in phagotcytosis
1- activation of neutrophil by inflammatory mediator
2- chemotaxis (follows trail to infection site)
3- recognition & adherence to bacterium (where opsonins help)
4- injestion (pseudopods form phagosome around bacteria)
5- killing & digestion (fuses with lysosome)
6- expulsion of undigestible parts
Interferon (IFN) production (innate defence process)
Only for viral infections
- interferes with viral replication
- 3 kinds: a, b and y
a,b and y IFN’s
a & b occur in cells infected by viruses
-a made by lymphocytes infected
b made by fibroblasts (connective tissue cell)
innate defence mechanisms adapted by immune system to provide ___.
highly specific defense mechanisms
How do interferons help the infected cell?
During viral replication, host cell products interferons. Infected cell releases them. Taken up by uninfected cells which then produce antiviral proteins from them. AVPs then interfere with viral protein synthesis, stemming the spread of the viral infection
