Lecture 14 - Structure and Function of Antibodies

Question 1

Describe the structure of an antibody

Answer 1

(Variable domain side by side->constant domain side by side->hinge region->constant domain one on top of another) x 2

Question 2

What is the heavy chain of an antibody

Answer 2

Inner half (variable domain->constant->hinge region->2 constant domains stacked)

Question 3

What is the light chain of an antibody

Answer 3

outer part (variable domain->constant domain)

Question 4

Five isotypes or classes of antibodies

Answer 4

1. IgG
2. IgM
3. IgD
4. IgE
5. IgA

Question 5

Where is the antigen binding site of an antibody

Answer 5

between the 2 variable domains on either side of an antibody

Question 6

Where is the Fab region on an antibody

Answer 6

Diagonal piece at top

Question 7

Where is the Fc region on an antibody

Answer 7

vertical piece at bottom

Question 8

How many polypoeptide chains do an antibody have

Answer 8

2 heavy chains and 2 light chains

Question 9

What are the different types of heavy chains

Answer 9

mu, delta, gamma, epsilon, alpha

Question 10

What do the heavy chains determine

Answer 10

the isotype of antibody

Question 11

Each molecule of the 2 identical light chains have either a ___ or ___

Answer 11

lambda or kappa (all five classes of antibodies use both kappa and lambda light chains)

Question 12

What hold the chains together and are also important in the structure of the domain loops

Answer 12

disulfide bonds

Question 13

What are domains

Answer 13

repeating homologous units that compose chains; composed of about 110 AA that fold into loops and held by a disulfide bond

Question 14

What is Fab (fragment antigen binding)

Answer 14

antigen binding end of the molecule, consists of the Vh, Ch1, VL, and CL domains

Question 15

What is the Fc (fragment crystallizable)

Answer 15

tail of the molecule, consists of CH2 and beyond

Question 16

What does Fc dictate

Answer 16

complement fixation, opsonization, binding of mast cells

Question 17

What is the antigen binding site

Answer 17

-consists of VH and VL domains
-binds to the epitope on the antigen

Question 18

What are within the antigen binding site VH and VL domains

Answer 18

hypervariable regions (CDRs)

Question 19

Antigen

Answer 19

stimulates an immune response

Question 20

Epitope

Answer 20

part of antigen that the antibody binds to; an antigen can have many epitopes

Question 21

Properties of antigen-antibody binding

Answer 21

1. non-covalent
2. electrostatic, H bonds, Van der Waals forces, hydrophobic bonds
3. reversible
4. goes to equilibrium
5. rapid

Question 22

Structure of IgG

Answer 22

four heavy chain domains

Question 23

Where is IgG found

Answer 23

blood stream and interstitital fluids; high conc in colostrum of large domestic species

Question 24

How much of total serum antibody does IgG make up

Answer 24

80% with half life of three weeks

Question 25

Important functions of IgG

Answer 25

-complement activation -neutralization of viruses and toxins -opsonization -systemic immunity in newborn -antibody dependent cell mediated cytotoxicity

Question 26

Structure of IgM

Answer 26

pentamer, heavy chain has 5 domains, held together by disulfide bonsd and J chain

Question 27

How many identical epitopes can IgM bind

Answer 27

10

Question 28

Where is IgM found

Answer 28

blood stream

Question 29

What is the first class of antibody produced in primary response

Answer 29

IgM

Question 30

Functions of IgM

Answer 30

1. complement activation 2. agglutination

Question 31

Relative amounts of IgM and IgG produced during the primary and secondary immune response

Answer 31

IgM predominates in primary immune response, IgG predominates in a later response

Question 32

Structure of IgA

Answer 32

4 heavy chain domains held togehter by a J chain

Question 33

Where is IgA found

Answer 33

-mucosal surfaces -secretory component added to molecule as it is transported to the mucosal surface -mother's milk

Question 34

Functions of IgA

Answer 34

-neutralize toxins and block entry of pathogens on mucosal surfaces -found in mother's milk and helps provide intestinal immunity to neonate

Question 35

IgE structure

Answer 35

-five domains in heavy chain, lot of polysaccharide attached to heavy chain -Fc portion has high affinity for the Fc receptor on mast cell

Question 36

What happens when binding of antigen to the IgE on mast cell

Answer 36

mast cell degranulation

Question 37

What can IgE activate also

Answer 37

eosinophils

Question 38

Where is most IgE found

Answer 38

mast cells, concentration in plasma is low

Question 39

functions of IgE

Answer 39

1. important in defense against helminthic parasites 2. Mediator of immediate hypersensitivity

Question 40

Where is IgD found

Answer 40

B cell surfaces

Question 41

IgD function

Answer 41

1. regulatory 2. B cell development