CMB1003/L23 Humoral Specific Immunity II

Question 1

What are the 2 types of light chains on antibodies?

Answer 1

Kappa or lambda

Question 2

What are the domains of the heavy chain on antibodies? (2)

Answer 2

C(H)1-3
V(H)

Question 3

What are the domains of the light chain on antibodies? (2)

Answer 3

C(L)
V(L)

Question 4

What is the domain of the glycosylated H chains on antibodies?

Answer 4

C(H)2

Question 5

Define the term ‘domain’.

Answer 5

Compactly folded globular units within proteins, often with evolutionary significance

Question 6

The domains found in Ig are also found in which other molecules involved in immunity? (3)

Answer 6

T cell receptor
MHC molecules
Various cell adhesion molecules
Signalling molecules

Question 7

Describe the structure of C(L) and V(L) domains. (4)

Answer 7

Compact immunoglobulin domains
100-110 amino acids
2 sheets of B strands
Intra-chain disulphide bond

Question 8

What are hypervariable (HV)/ complementary-determining regions (CDR)? (3)

Answer 8

3 loops of HV on each H and L chain
6 CDR form the antigen binding sites
Framework (other loops and strands) less variable

Question 9

What do the C domains control?

Answer 9

Effector function of Ig

Question 10

What are the 5 heavy chain isotypes of antibodies?

Answer 10

Mu/ IgM
Delta/ IgD
Gamma/ IgG
Epsilon/ IgE
Alpha/ IgA

Question 11

What is the functional difference between kappa and lambda light chains?

Answer 11

None

Question 12

What are the macro structures of the 5 isotypes?

Answer 12

IgG, IgD, IgE simple
IgA forms a dimer
IgM forms a pentamer

Question 13

Describe the structure of IgM. (3)

Answer 13

Mew chains
5 domains
No hinge
(Mew2L2)5 covalently bound to J chain

Question 14

What is the valency of IgM?

Answer 14

10

Question 15

Describe the affinity of IgM. (2)

Answer 15

First response
Relatively low affinity as pre-affinity maturation

Question 16

What is the function of IgM? (4)

Answer 16

Monomer present on B cell surface (BCR) during B cell development
Activates complement
Agglutination
Protects from common pathogens

Question 17

Describe the structure of IgD. (4)

Answer 17

Present on B cell surface during B cell development
Delta2L2
Delta chain
4 domains
Long hinge

Question 18

What is the function of IgD?

Answer 18

Largely unknown

Question 19

Describe the structure of IgG. (4)

Answer 19

Gamma2L2
Gamma chains
4 domains
Most prevalent class in serum
Production increased in secondary responses

Question 20

Describe the differences in the sub-classes of IgG.

Answer 20

Differ in hinge regions

Question 21

What is the function of IgG? (4)

Answer 21

Large increase in secondary response
Complement activation
Opsonisation
ADCC
Crosses placenta

Question 22

Describe the structure of IgA. (4)

Answer 22

Alpha2L2
Alpha chains
4 domains
Hinge
Monomer in serum
Dimer in secretions bound to J chain and secretory component

Question 23

What is the difference in the subclasses of IgA?

Answer 23

IgA1 - predominant serum
IgA2 - found in secretions

Question 24

What is the function of IgA? (4)

Answer 24

Most abundant Ig around mucosal membrane
Inhibition of microbial adherence
Neutralise toxins and pathogens
Prevent commensal bacteria from entering bloodstream
Intestinal protection of neonate

Question 25

Describe how IgA accesses the gut lumen. (3)

Answer 25

Dimeric IgA is transported into gut lumen through epithelial cells as base of crypts Dimeric IgA binds to layer of mucus overlying gut epithelium IgA in gut neutralises pathogens and their toxins

Question 26

Describe the structure of IgE. (3)

Answer 26

Epsilon2L2 Epsilon chain 5 domains Lowest concentration of Ig in serum

Question 27

Describe the action of IgE. (2)

Answer 27

Binds with high affinity to FcR on mast cells & basophils Releases vasoactive/inflammatory mediators

Question 28

What is the function of IgE? (3)

Answer 28

ADCC Protection against helminth and protozoa infection Induces eosinophils and basophils to release histamine and proteases Role in allergy and asthma

Question 29

Describe the role of IgE in allergy. (2)

Answer 29

Resting mast cell has granules that contain histamine and other inflammatory mediators Multivalent antigen cross-links bound IgE antibody, causing release of granule contents

Question 30

Describe the series of events following IgE binding to Fc receptors on mast cells and basophils. (3)

Answer 30

Increased histamine release Increased TNFa Increased vasodilation

Question 31

How does epinephrine (EpiPen) stop anaphylaxis? (2)

Answer 31

Increased vasoconstriction Increased blood glucose levels

Question 32

Where is IgG and IgM predominantly found?

Answer 32

In blood

Question 33

Where is IgG and IgA predominantly found?

Answer 33

Extracellular fluid

Question 34

Where in the body is devoid of Ig?

Answer 34

Brain

Question 35

Where is IgA predominantly found?

Answer 35

Secretions (mucosal membrane) and breast milk

Question 36

Which form of Ig does the foetus receive from the mother?

Answer 36

IgG

Question 37

Which Ig is associated with mast cells just below epithelial surfaces?

Answer 37

IgE

Question 38

Describe how B cells are able to produce different Ig isotypes. (3)

Answer 38

During development, IgM & IgD is produced As immune response progresses, B cells isotype switch appropriately Isotype switching involves irreversible DNA recombination