Antibody Structure and Function

Question 1

Where do B cells arise and what do they do when they mature?

Answer 1

They arise from bone marrow stem cells and exit the bone marrow and enter circulation to search for antigens after maturation

Question 2

What are the functions of antibodies (7)?

Answer 2

Neutralization of microbes and toxins
Opsonization and phagocytosis of microbes
Antibody-dependent cellular cytotoxicity
Lysis of microbes
Phagocytosis of microbes opsonized with complement fragments
Inflammation
Complement activation

Question 3

What are two characteristics of antigen/BCR interactions?

Answer 3

BCR detect 3D antigens
B cells are only active against extracellular antigens

Question 4

What is a clone?

Answer 4

A parental lymphocyte and all of its progeny

Question 5

What are antibodies?

Answer 5

A type of glycoprotein produced by B cells

Question 6

How do antibodies bind antigens?

Answer 6

With a high degree of specificity and affinity

Question 7

What is the structure of an antibody?

Answer 7

Two light chains and two heavy chains
Light chains are connected to heavy chains by a disulfide bond
Heavy chains are connected by 2 disulfide bonds

Question 8

What do light chains contain?

Answer 8

One V domain and one C domain

Question 9

What do heavy chains contain?

Answer 9

One V domain and at least 3 C domains

Question 10

Where do antibodies bind antigens?

Answer 10

Through the variable regions by reversible non-covalent interactions

Question 11

What is the V region involved in?

Answer 11

Antigen recognition

Question 12

What is the C region involved in?

Answer 12

Structural integrity and effector functions

Question 13

What is an epitope?

Answer 13

The parts of an antigen recognized by an antibody
Can be recognized on the basis of sequence or shape

Question 14

What is affinity?

Answer 14

The strength with which one antigen-binding surface of an antibody binds an antigen

Question 15

What are the 4 features of antibody-mediated antigen recognition?

Answer 15

Antibodies recognize a large array of 3D structures
Each clone is specific for a single antigen
Antigen recognition is mediated by specific domains of the antibody
Signaling triggers B cell activation

Question 16

What are 2 IgA molecules joined by?

Answer 16

A J chain

Question 17

What does the J chain facilitate?

Answer 17

Transport of IgA across the mucosal epithelia and the transfer of IgA to newborns

Question 18

What are the functions of IgA?

Answer 18

Mucosal immunity
Neonatal passive immunity

Question 19

What is the function of IgD?

Answer 19

Found on naive B cells and acts as a marker for B cell development

Question 20

How is IgE secreted and where does it bind?

Answer 20

It is secreted as a monomer and binds to the Fc(epsilon) receptor on mast/basophilic cells

Question 21

What are the functions of IgE?

Answer 21

Binds allergens and facilitates degranulation
Facilitates protection against parasites
Possible role in cancer immunity

Question 22

How is IgG secreted and where is it found?

Answer 22

Secreted as a monomer and found in bodily fluid

Question 23

Which immunoglobulin can be transferred to a fetus?

Answer 23

IgG

Question 24

What are the functions of IgG?

Answer 24

Neutralization of toxins
Opsonization for inducing phagocytosis via complement system
Facilitates antibody-dependent cytotoxicity on NK cells

Question 25

What is unique about IgE?

Answer 25

It has an extra C region

Question 26

How is IgM secreted and what chain assists with secreted?

Answer 26

Pentamer and J chain

Question 27

How many binding sites does IgM have?

Answer 27

10

Question 28

What is the first antibody expressed in mature B cells?

Answer 28

IgM

Question 29

What is the function of IgM?

Answer 29

Complement pathway activation (neutralization, phagocytosis)