Exam 2: Dr. Pharr Antibody Structure and B-cell Development

Question 1

What is an immunoglobulin composed of?

Answer 1

2 identical heavy chains
2 identical light chains
Variable region
Hinge region
Constant region

Question 2

What is the light chain composed of?

Answer 2

A single variable domain and a single constant domain

Question 3

What is the heavy chain composed of?

Answer 3

A single variable domain and three to four constant domains

Question 4

What does the variable region do?

Answer 4

Antigen recognition

Question 5

What is the hinge region?

Answer 5

Flexible polypeptide structure

Question 6

What does the constant (Fc) region do?

Answer 6

Determines the effector function of the antibody

Question 7

What is the constant region recognized by?

Answer 7

Leukocytes and plasma proteins

Question 8

What are the 5 classes of antibodies defined by?

Answer 8

Heavy chain constant region

Question 9

What are the 5 classes of antibodies?

Answer 9

IgG
IgA
IgM
IgD
IgE

Question 10

In a primary immune response, wha is the first antibody produced?

Answer 10

IgM

Question 11

What is it called when later in the immune response additional isotypes are produced?

Answer 11

Isotype switching

Question 12

Why is it important that the B cell receptor recognizes the native form of an antigen?

Answer 12

The antibody will link the pathogen to the leukocytes and plasma proteins that will eliminate it

Question 13

What is an epitope?

Answer 13

The part of the antigen bound by the antibody

Question 14

What can an epitope consist of?

Answer 14

A cluster of amino acids or a portion of a polysaccharide

Question 15

What can a pathogen express on the surface?

Answer 15

A number of complex proteins and carbohydrates

Question 16

What must the shape of the antigen binding site be complementary to?

Answer 16

The shape of the the epitope

Question 17

What is cross-reactivity?

Answer 17

The binding of an antibody to an antigen not used to generate that antibody

Question 18

What are the reasons for cross-reactivity?

Answer 18

Shared epitope (different antigens share the same epitope)
Similar epitope (pathogens express protein or carbohydrate epitopes that resemble host epitopes)

Question 19

What are polyclonal antibodies?

Answer 19

A mixture of antibodies, each specific for a different epitope from the same antigen

Question 20

What is a monoclonal antibody?

Answer 20

Antibody originating from a single B cell

The antibody is specific for one epitope

Question 21

What does the mechanism of immunoglobulin development ensure?

Answer 21

That each lymphocyte expresses an immunoglobulin of a single antigen specificity

Question 22

What is somatic recombination?

Answer 22

DNA recombination that occurs between gene segments in the immunoglobulin genes

Question 23

How does the process of somatic recombination contribute to the diversity of antigen-binding sites?

Answer 23

There are multiple copies of gene segments in the light chain gene and the heavy chain gene

Question 24

What is the construction of the antigen binding site by somatic recombination like?

Answer 24

1. Gene segments are used construct the variable region of the light chain gene and the heavy chain gene
2. The gene segments differ from one another in short regions called hypervariable regions
3. Somatic recombination results in the random additional nucleotides at the joints between gene segments

Question 25

What is the bone marrow responsible for?

Answer 25

Development of B cells

Question 26

What is the development of B cells like?

Answer 26

Diverse repertoire of naive B cells produced in the bone marrow–somatic recombination

Question 27

What is central tolerance?

Answer 27

Removal of immature B cells with specificity for self-proteins

Question 28

What type of B cells will be transported into the blood from bone marrow?

Answer 28

B cells tolerant to self proteins

Question 29

What happens during surveillance with naive B cells?

Answer 29

Naive B cells are exported to the periphery to circulate through secondary lymphoid tissues

Question 30

What happens during the primary immune response to an infection?

Answer 30

1. Recognition of antigen
2. Activation by helper T cells
3. Differentiation to short-lived plasma cells

Question 31

In a primary immune response, IgM is secreted as a pentamer. Why?

Answer 31

IgM generally possesses low affinity for the antigen epitope. However, the pentameric structure increases the valence from 2 antigen binding site to 10 antigen binding sites