Immunoglobulins

Question 1

what is another word immunoglobulin

Answer 1

antibody

Question 2

immunoglobulins are present where? 4

Answer 2

plasma, tissues, secretions and lymphatics

Question 2

immunoglobulins are a product of which immune system?

Answer 2

humoral

Question 2

immunoglobulins are secreted by what?

Answer 2

plasma cells - activated B cells

Question 2

what are the 5 classes of immunoglobulins?

Answer 2

IgG
IgM
IgA
IgD
IgE

Question 3

annotate this diagram of immunoglobulin structure with the following regions
- variable region
- constant region
- heavy chain
- light chain
-Fab
- Fc
- Hinge
- disulphide bonds

Answer 3

Question 4

antibodies have dual function, what are the functions?

Answer 4

recognition function - Fab region binding to antigen

effector function - clearing mechanism - Fc region interacting with effector molecules

Question 5

what are the two types of light chain that are used in all antibody classes?

Answer 5

lambda
kappa

Question 6

in any individual antibody molecule, both light chains are?

Answer 6

the same

Question 7

light chains fold up into 2 globular domains termed what?

Answer 7

VL - variable light domain
CL - constant light domain

Question 8

what determines the class of antibody?

Answer 8

heavy chain

Question 9

in IgG what is the type of heavy chain?

Answer 9

γ gamma

Question 10

in IgA what is the type of heavy chain?

Answer 10

α alpha

Question 11

in IgM what is the type of heavy chain?

Answer 11

μ mu

Question 12

in IgD what is the type of heavy chain?

Answer 12

δ delta

Question 13

in IgE what is the type of heavy chain?

Answer 13

ε epsilon

Question 14

heavy chains fold up into 4 (or 5) globular domains, what are they starting from N terminus?

Answer 14

VH - variable heavy
CH1 - constant heavy 1
CH2
CH3
(CH4)

Question 15

annotate this image with the domains

Answer 15

Question 16

what holds the domains together in an immunoglobulin?

Answer 16

non-covalent interactions between: VL-VH, CL-CH1, CH3-CH3

oligosaccharides between CH2-CH2 (less closely linked)

Question 17

in the VL and VH domain there are 3 parts in the amino acid sequence that determine the what antigen a specific antibody will bind to what are these areas called?

Answer 17

hypervariable loops 1,2, and 3
or
complementary determining regions CDR1,2, and 3

Question 18

when the VH and VL domains are paired their 6 CDRs create what?

Answer 18

the antigen binding site

Question 19

what does epitope mean?

Answer 19

actual structural part of the antigen that is recognised

Question 20

what is the most abundant immunoglobulin in plasma?

Answer 20

IgG

Question 21

what is the structure of IgG?
Shape, number of HC and LC and subclasses

Answer 21

Y shaped
2HC and 2LC
4 subclasses IgG1,2,3 and 4

Question 22

IgG is very efficient at triggering ? and ? via ?

Answer 22

complement phagocytosis Fc receptors

Question 23

what is the only Ig class to pass the placenta from mother to foetus? why is this important?

Answer 23

IgG protects baby in the first months of life because there is a lag where the baby cant make its own IgG

Question 24

IgG is the predominant antibody of the primary or secondary immune response?

Answer 24

secondary

Question 25

IgM is found where?

Answer 25

only in plasma and secretions, its too large to enter tissues

Question 26

what is the structure of IgM?

Answer 26

5 Y shaped units joined by a joining chain (J chain- extra polypeptide) and disulphide bridges heavy chain has 5 globular domains

Question 27

how does the structure of IgM relate to its function?

Answer 27

10 binding sites mean that it is very good at linking onto numerous particles and clumping viruses together - agglutination

Question 28

IgM is very efficient at activating what?

Answer 28

complement

Question 29

IgM is the predominant antibody of the primary or secondary immune response?

Answer 29

primary

Question 30

Human IgA is the major antibody in what?

Answer 30

seromucous secretions e.g. saliva, milk, colostrum, gut, tracheobronchial system and genito-urinary system

Question 31

what is the class of antibody first encountered by many invading bacteria and viruses

Answer 31

Human IgA

Question 32

what are the subclasses of IgA in humans?

Answer 32

IgA1 and IgA2

Question 33

serum IgA is predominantly in monomeric or dimeric form?

Answer 33

monomeric 90% IgA1 10% IgA2

Question 34

secretory IgA is predominantly monomeric or dimeric?

Answer 34

dimeric 40% IgA1 60% IgA2

Question 35

in secretory IgA which is predominantly dimeric there is an additional polypeptide. what is it called and what does it do?

Answer 35

secretory component helps protect the secretory IgA in the harsh environment of secretions e.g. extreme pH or proteolytic enzymes.

Question 36

recognise this

Answer 36

Question 37

recognise this

Answer 37

Question 38

what is the structure of IgE

Answer 38

y shaped 5 globular domains in each heavy chain lots of N linked oligosaccharides (sugars)

Question 39

what does IgE do?

Answer 39

interacts with Fc receptor FcεR1 -> expressed on mast cells and basophils and is associated with the allergic response (due to high affinity) important in protection against parasitic infections

Question 40

where is IgD mostly found?

Answer 40

on the surface of lymphocytes

Question 41

what is the function of IgD?

Answer 41

unclear - thought to be involved in the control of antibody response

Question 42

what are the key effector molecules that immunoglobulins interact with?

Answer 42

Fc receptors complement

Question 43

what are Fc receptors?

Answer 43

receptors that bind specifically to the Fc region of immunoglobulins

Question 44

what are the Fc receptors that are specific to IgG Fc region?

Answer 44

FcγRI, FcγRII, FcγRIII

Question 45

what are the Fc receptors that are specific to IgA Fc region?

Answer 45

FcαR

Question 46

what are the Fc receptors that are specific to IgE Fc region?

Answer 46

FcεRI , FcεII

Question 47

what happens when an Fc receptor binds to the Fc region of an immunoglobulin

Answer 47

invading pathogen has many antibodies that bind to it resulting in multiple Fc receptors being engaged at the same time. - phagocytosis - release of activated oxygen species and enzymes - release of inflammatory mediators e.g. histamine - enhanced antigen presentation - clearance of immune complexes

Question 48

release of the inflammatory mediator histamine is triggered by what receptor? what releases it?

Answer 48

FcεRI released from mast cells and basophils