Antibody Structure and Function Flashcards
Where do B cells arise and what do they do when they mature?
They arise from bone marrow stem cells and exit the bone marrow and enter circulation to search for antigens after maturation
What are the functions of antibodies (7)?
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
What are two characteristics of antigen/BCR interactions?
BCR detect 3D antigens
B cells are only active against extracellular antigens
What is a clone?
A parental lymphocyte and all of its progeny
What are antibodies?
A type of glycoprotein produced by B cells
How do antibodies bind antigens?
With a high degree of specificity and affinity
What is the structure of an antibody?
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
What do light chains contain?
One V domain and one C domain
What do heavy chains contain?
One V domain and at least 3 C domains
Where do antibodies bind antigens?
Through the variable regions by reversible non-covalent interactions
What is the V region involved in?
Antigen recognition
What is the C region involved in?
Structural integrity and effector functions
What is an epitope?
The parts of an antigen recognized by an antibody
Can be recognized on the basis of sequence or shape
What is affinity?
The strength with which one antigen-binding surface of an antibody binds an antigen
What are the 4 features of antibody-mediated antigen recognition?
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
What are 2 IgA molecules joined by?
A J chain
What does the J chain facilitate?
Transport of IgA across the mucosal epithelia and the transfer of IgA to newborns
What are the functions of IgA?
Mucosal immunity
Neonatal passive immunity
What is the function of IgD?
Found on naive B cells and acts as a marker for B cell development
How is IgE secreted and where does it bind?
It is secreted as a monomer and binds to the Fc(epsilon) receptor on mast/basophilic cells
What are the functions of IgE?
Binds allergens and facilitates degranulation
Facilitates protection against parasites
Possible role in cancer immunity
How is IgG secreted and where is it found?
Secreted as a monomer and found in bodily fluid
Which immunoglobulin can be transferred to a fetus?
IgG
What are the functions of IgG?
Neutralization of toxins
Opsonization for inducing phagocytosis via complement system
Facilitates antibody-dependent cytotoxicity on NK cells
What is unique about IgE?
It has an extra C region
How is IgM secreted and what chain assists with secreted?
Pentamer and J chain
How many binding sites does IgM have?
10
What is the first antibody expressed in mature B cells?
IgM
What is the function of IgM?
Complement pathway activation (neutralization, phagocytosis)
