Antibodies Part 1

Question 1

In antibodies, each chain is composed of domains helpd together by what?

Answer 1

intrachain disulfide bonds

Question 2

What are the domains of the light chain? heavy chain?

Answer 2

light: one variable and one constant
heavy: on variable and three constant

Question 3

In IgG, what pushes the CH2 domains of the heavy chains out a little bit to help them interact with components of the complement system?

Answer 3

a patch of carbohydrates

Question 4

IgM forms a ___amer,

Answer 4

pentamer

Question 5

What’s the chain holding the globulin units together in IgM?

Answer 5

J chains

Question 6

What is IgM particularly good at?

Answer 6

activating complement

Question 7

What’s an important distinction about IgA (besides the fact that it’s a dimer of globulin units)?

Answer 7

It has a secretory component that will keep it from being degraded by the secretions in the mucous membranes

Question 8

Where are IgD located?

Answer 8

on the membranes on B cells - act as the BCR

Question 9

Are the heavy chains always identical in antibodies? the light chains?

Answer 9

They are identical within the same antibody, yes.

Question 10

What are the 5 kinds of heavy chains that define the class of natibody?

Answer 10

gamma, alpha, mu, epsilon, and delta

Question 11

What are the two varieties of light chains?

Answer 11

kappa and lambda

Question 12

During class switching (like going from making IgM to IgA for example), what changes: the light chains or heavy chains?

Answer 12

only the heavy chains switch - the light chains sill stay the same

Question 13

The area at the N terminal of the antibody is called what domain?

Answer 13

the variable domain

Question 14

Aminoa acid sequence variability is not distributed uniformly along the variable domain; most of the variability is in 3 areas called the _______ regions or _____-determining regions since they make the actual antigen binding site

Answer 14

hypervariable regions

complementarity-determining regions

Question 15

What does valence refer to?

Answer 15

the number of antigenic determinants (epitopes) an antibody molecule can theoretically bind

Question 16

What’s the valence of IgG? IgA? IgM? Fab? isolated VL or VH?

Answer 16

IgG = 2
IgA = 4
IgM = 10
Fab = 1
Vl or VH = 0 (it takes the combo of the two chains

Question 17

What is the concentration of the 5 classes of antibodies in the serum?

Answer 17

IgG = 1000 mg/dL
IgA= 200 mg/dL
IgM = 100 mg/dL
!gD = 5 mg/dL
IgE = 0.02 mg/dL

Question 18

What antibody is the main one in blood and tissue fluids?

Answer 18

IgG

Question 19

What can IgG do?

Answer 19

It can neutralize toxins and blood-borne iruses, binds bacteria and facilitates their destruction by activating complment and by binding them to phagocytic cells

Question 20

Where is IgA primarily located?

Answer 20

in secretions (does pretty much the same thing as IgG)

Question 21

What is the first antibody to appear in the serum after immunization?

Answer 21

IgM

Question 22

Although it is very efficient at activating complement, why is it less adept than IgG at other functions?

Answer 22

It does not get into tissue fluids very efficiently, nor is it bound efficiently by phagocytic cells

Question 23

What type of hypersensitivity is associated with and IgE mediated process?

Answer 23

type 1 hypersensitivity (allergies)

Question 24

Althouhg IgE is associated with allergies, what is it’s true importance for the immune system?

Answer 24

resistance to worms and other parasites

Question 25

When an IgG or IgM antibody binds antigen, there can be a change in the angle between the two Fab pieces which causes a bulging of the structure of the Fc part so that….

Answer 25

1. they can bind to phagocytic cells which have receptors for the altered Fc of IgG
2. Clq (first component of complement) can bind to the Fc and be activated

Question 26

Why is IgM so much better than IgG at activating complement?

Answer 26

Because IgM is a pentamer, it only needs one IgM molecule to activate complement, while IgG will have to have multiple binding close together on the same surface

Question 27

Describe how the immunoglobulin genes are organized in the chromosome

Answer 27

They’re organized from 5’ to 3’: V (variable regions), then D (differentiating regions), then J (joining regions)

Question 28

Describe the general mechanism by which the variable regions undergo gene rearrangement.

Answer 28

in the nucleus of the cell, the V, D, and J domains can be recombined at random

for the heavy chains you’ll get 1 V, 1 D and 1 J eventually linked together (everything else is spliced) formign a functional VDJ gene

For the light chains it’s similar, but you only have a V and J (no D)

Question 29

What enzymatic complex is needed for recombination to occur?

Answer 29

RAG synatpic complex

Question 30

How many subclasses of antibodies are there? What are they?

Answer 30

there are ten

IgG1, IgG2, IgG3, IgG4
IgA1, IgA2
IgM1, IgM2
IgD
IgE

Question 31

The allelic differences in the sequences of immunoglobulins between individuals are called what?

Answer 31

allotypes

Question 32

Each antibody will have its own unique combining region which we call the…

Answer 32

idiotype

Question 33

An antibody that actually recognizes the idiotype of another antibody is called what?

Answer 33

an anti-idiotype