antibodies and B lymphocytes

Question 1

how many hypervariable regions in the Fab

Answer 1

3

Question 2

what are complementarity determining regions (hypervariable regions)

Answer 2

loops of amino acis which bind to epitope of antigen, lining up at end of V domains

Question 3

what is the structure of the constant region

Answer 3

barrel-shaped B-pleated sheets with internal disulphide bridges

Question 4

why is a large number of interactions between antibody and epitope important

Answer 4

forces are non-covalent so are weak

Question 5

define antibody affinity

Answer 5

strength of total non-covalent interactions between a single Fab and single epitope on antigen

Question 6

define antibody avidity

Answer 6

overall strength of multiple interactions between an antibody with multiple binding sites and a complex antigen with multiple epitopes

Question 7

antibody avidity vs affinity

Answer 7

avidity is a better measure of binding capacity

Question 8

define antibody cross-reactivity

Answer 8

antibodies elicit in response to one antigen can sometimes recognise a different antigen of similar structure (e.g. smallpox and cowpox, ABO blood group antigens)

Question 9

what are the 5 classes of antibodies (Ig)

Answer 9

G, A, M, E, D

Question 10

which 2 classes of antibodies have subclasses, and what does this mean

Answer 10

IgG, IgA; subtly differeny functions and body locations

Question 11

what is different and the same in the 5 classes of antibodies

Answer 11

different heavy chains and CH domains, same light chains (K, λ)

Question 12

what is the most abundant Ig

Answer 12

IgG

Question 13

IgG: what is the heavy chain

Answer 13

y

Question 14

IgG: how many monomer subclasses

Answer 14

4

Question 15

IgG: where is variability mainly located

Answer 15

hinge region, effector function domains

Question 16

which Ig is actively transported across the placenta

Answer 16

IgG

Question 17

IgG: where is it located

Answer 17

blood, EC fluids

Question 18

IgG: what subsets are the major activators of classical complement pathway

Answer 18

IgG1, IgG3

Question 19

what is the major secretory Ig

Answer 19

IgA

Question 20

IgA: what is the heavy chain

Answer 20

a

Question 21

what is the 2nd most abundant Ig

Answer 21

IgA

Question 22

IgA: where does it occur as monomers, and dimers

Answer 22

monomer: blood; dimer: secretions

Question 23

IgA: function

Answer 23

protects mucosal surfaces from bacteria, viruses, protozoa

Question 24

what is the first Ig synthesised after exposure to anigen

Answer 24

IgM (acts in primary antigen response)

Question 25

IgM: what is the heavy chain

Answer 25

u

Question 26

IgM: binding sites

Answer 26

multiple (10 Fab regions as large pentameric molecule joined by J chain), so compensate for low affinity

Question 27

IgM: location

Answer 27

blood as large

Question 28

IgM: function

Answer 28

multiple binding sites so efficient as agglutination and activating complement

Question 29

IgE: what is the heavy chain

Answer 29

E

Question 30

IgE: when is it produced

Answer 30

present at very low concentrations in response to parasitic infections and in allergic diseases

Question 31

IgE: what does it bind to

Answer 31

high affinity Fc receptors of mast cells and basophils

Question 32

IgE: what does cross-linking by antigen trigger

Answer 32

mast cell activation and histamine release

Question 33

IgD: what is the heavy chain

Answer 33

d

Question 34

IgD: concentration

Answer 34

very low concentration as serum (not much soluble IgD)

Question 35

IgD: when is surface IgD expressed

Answer 35

early in B cell development

Question 36

IgD: what is it involved with

Answer 36

B cell development and activation

Question 37

comparison of Ig structures

Answer 37

diagram

Question 38

which Ig are present in blood

Answer 38

IgG, IgM

Question 39

which Ig is present in EC fluid

Answer 39

IgG

Question 40

which Ig is present in secretions

Answer 40

dimeric IgA

Question 41

which maternal Ig is present in foetus via placenta

Answer 41

IgG

Question 42

which Ig is present with mast cells below epithelia

Answer 42

IgE

Question 43

5 consequences of antibody-antigen binding

Answer 43

neutralisation, agglutination, opsonisation, complement activation, bound by cells expressing Fc receptors (especially innate immunity such as phagocytes and NK cells)