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)
