Immunology 1: Immune system & its Defence mechanisms

Question 1

The immune system provides defence against?

Answer 1

microbial pathogens & cancer

Question 2

Three characteristics of immune responses?

Answer 2

Specificity, universality & adaptability

Question 3

What does specificity encompass?

Answer 3

Immune response that’s able to contain one microbial pathogen isn’t effective against 2nd microbe unless the 2 are closely related

Question 4

What does universality encompass?

Answer 4

• immune system can respond to whole universe of foreign substances
• immune system can attack virtually all microbes

Question 5

What does adaptability refer to?

Answer 5

• immune responses take time to develop (1-2 weeks)

- defences provides by response not present at time of first infection

Question 6

Primary & secondary immune responses?

Answer 6

• primary follows primary infection
• 2ndary follows 2ndary infection
• 2ndary response faster & more intense than 1st (why vaccinations work)

Question 7

2ndary response example of?

Answer 7

positive memory

Question 8

Negative memory example?

Answer 8

pre-exposure to antigen results in lessened ability to respond to subsequent challenge of antigen

Question 9

immune systems first seen in?

Answer 9

lower vertebrate animals

-newer evolutionary trait

Question 10

innate resistance?

Answer 10

• 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

Question 11

Innate defence mechanisms are ___ where as immune responses are ____.

Answer 11

constitutive; inducible (form of adaptability)

Question 12

3 defence systems of a vertebrate?

Answer 12

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

Question 13

3 characteristics of innate defence?

Answer 13

• immediate protection
• non specific
• constitutive or uninductible

Question 14

4 processes of innate defence?

Answer 14

inflammation, phagocytosis, processes initiated by compliment, interferon production.

Question 15

Acute inflammation (innate defence process)

Answer 15

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

Question 16

Role of histidine in acute inflammation?

Answer 16

• stored in mast cells
• released at site of injury causing local inflammation in area!
• central role in initiating inflammatory response

Question 17

Phagocytosis (innate defence process)

Answer 17

• 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

Question 18

Processes initiated by complement (innate defence process)

Answer 18

• 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

Question 19

complement cascade initiation?

Answer 19

• classical: discovered first, more evolutionarily recent. Part of immune response
• alternative: part of innate defence

Question 20

How are complement components involved in innate defence?

Answer 20

• 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)

Question 21

What happens if a phagocyte cannot adhere to bacterium?

Answer 21

linking molecules (opsonins) facilitate by building bridge b/n phagocyte & bacteria

Question 22

Steps in phagotcytosis

Answer 22

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

Question 23

Interferon (IFN) production (innate defence process)

Answer 23

Only for viral infections

• interferes with viral replication
• 3 kinds: a, b and y

Question 24

a,b and y IFN’s

Answer 24

a & b occur in cells infected by viruses
-a made by lymphocytes infected
b made by fibroblasts (connective tissue cell)

Question 25

innate defence mechanisms adapted by immune system to provide ___.

Answer 25

highly specific defense mechanisms

Question 26

How do interferons help the infected cell?

Answer 26

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