Antibodies - Diebel

Question 1

Basic structure of an antibody

Answer 1

• Fab region (basic unit) = 2 heavy chains and 2 light chains
• Fc region = 2 heavy chains

Question 2

H chain

Answer 2

5 kinds: gamma, alpha, mu, epsilon, delta

-defines the class of antibody to which the molecule belongs

Question 3

L chain

Answer 3

2 varieties: kappa or lambda

Question 4

What chain changes in class switching?

Answer 4

Heavy chain!

Question 5

Secreted IgA structure?

Answer 5

Dimer of the basic unit (2 H’s and 2 L chains)

Basic units held together by J chain

Question 6

IgM structure?

Answer 6

Pentamer

Basic units held together by J chain

Question 7

Constant Region

Answer 7

Made up of 1 to 4 compact, structurally-similar domains call C domains

Question 8

Variable Domains

Answer 8

Different in sequence between antibodies of different specificities.

-At N-terminal

Hyper variable regions make it more different

Question 9

Valence=

Answer 9

of antigenic determinates (epitopes) an antibody molecule can theoretically bind.

Question 10

Valence of IgG

Answer 10

2 (1 antibody with 2 Fab parts)

Question 11

Valence of secreted IgA

Answer 11

4

Question 12

Valence of IgM

Answer 12

10 in theory but 5 in practice b/c of puckering

Question 13

Valence of Fab?

Answer 13

1

Question 14

Valence of F(ab’)2:

Answer 14

2

Question 15

Valence of isolated VL or VH?

Answer 15

0 –takes a combo of VL and VH to make antibody binding sites

Question 16

Isotypes:

Answer 16

• Constant domains change but variable domains stay the same
• slight differences in the AA sequence of their H chain C regions

Question 17

10 isotypes

Answer 17

IgG 1-4
IgA 1-2
IgM 1-2
IgD
IgE

Question 18

Allotypes

Answer 18

• minor ALLELIC differences in sequence of Igs between individuals
• depends on if you are using your mom or dad’s genes to produce chain

Ex: two IgG1 molecules that are the same but the AA sequence is slightly different

Question 19

Idiotypes

Answer 19

=unique combining region, made up of the CDR (complementarity- determining regions) amino acids of its L and H chains

• Antigen determinate part of Ab
• *Antibody’s unique combining site considered as an antigen.

Question 20

CDR (complementarity-determining regions)

Answer 20

AA sequence variablity is not distributed uniformly along V domain

• These 3 areas are called CDR or hypervariable regions
• CDR comprise the actual antigen-binding site

Question 21

Anti-idiotype

Answer 21

Antibodies made that recognize the unique sequence of that combining site and no other.

Question 22

IgG (1000 mg/dL)

Answer 22

• main antibody in blood and fluids
• Neutralizes toxins and blood-borne viruses,
• activates complement to destroy bacteria

-main antibody! - memory

Question 23

IgA (200 mg/dL)

Answer 23

Does same as IgG in blood

• Real work is SECRETIONS
• Forms a DIMER and secretory components protects it from proteolysis

Question 24

IgM (100 mg/dL)

Answer 24

• same as IgG
• FIRST antibody to appear in serum after immuniztion
• very efficient at activating complement

Question 25

IgD (5 mg/dL)

Answer 25

role uncertain - functions mainly as receptor on naive B cells - always surface bound

Question 26

IgE (0.02 mg/dL)

Answer 26

Causes Type 1 immunopathology (immediate hypersensitivity) - ALLERGIES - BUT true importance is in resistance to WORMS/PARASITES

Question 27

2 things initiated after antibody binds an antigen?

Answer 27

IgG or IgM binds to antigen and conformational change happens so 2 things are initiated: 1. Binding to phagocytic cells - have receptors FcR for the altered Fc of IgG 2. C1q (1st part of the complement system) now binds to 2 adjacent Fcs and is ACTIVATED

Question 28

IgG activation of Complement

Answer 28

Secreted as a monomer but forms a HEXAMER to activate complement

Question 29

IgG1 structure

Answer 29

Disulfide bonds hold chains together | 3 constant heavy domains

Question 30

IgG3 structure

Answer 30

Monomer | -larger hinge region so it is better at binding complement than IgG1

Question 31

IgM structure

Answer 31

Secreted form: - 5 antibodies linked by J chain = PENTAMER - 4 constant heavy domains

Question 32

IgA structure

Answer 32

Dimer (linked by J chain) | Secretory component that helps it go through epithelial cell layers

Question 33

IgD structure

Answer 33

ONLY membrane bound - only on naive B cells - monomer

Question 34

IgE structure

Answer 34

- 4 constant heavy domains | - always secreted as a monomer