Immunoglobulin Structure Flashcards
What is the general structure of antibodies?
Antibodies have 2 light and 2 heavy chains
and they are identical and held together by
disulfide bonds
What part of the antibody is variable and reacts to antigens?
The N terminal end of the antibody
How many antigens can one antibody bind?
Two as there are two sites
How many types of antigens can an antibody bind?
One
How many types of antibodies can a single antigen bind
Many
What separates the classes of antibodies?
Antibody classes differ based on the constant
region of the antibody
What is Fab?
Fab - antigen binding fragment
What is Fc?
Fc - crystallized fragment (constant fragment)
What are the classes of antibodies?
IgG IgA IgM IgE IgD
What is the function of the hinge region?
Flexibility in binding antigens
What structure is IgM often found as?
Pentameric with the J chain
What structure is IgA often found as?
Dimeric with J chain
Where is IgA found as a monomer?
In the blood
Where is IgA found as a dimer?
Mucosal areas like eyes, nasal area and gut -> known as secretory IgA
What is the function of the secretory component on dimeric IgA?
Protects IgA from proteolytic secretions in the stomach and gut
What antibody class is not found in the serum?
IgD
Where is IgD found?
IgD is antibodies on surface of B cells
What is the major antibody class in the blood?
IgG
What is the only antibody class to cross the placenta?
IgG
What is IgE responsible for?
Allergies
How does IgE cause allergies?
IgE binds to mast cells but nothing happens with IgE bound until an allergen binds and cross linking occurs between the IgEs then degranulation of the mast cells occurs
What is the predominant Ab induced in primary response?
IgM
What is the predominant Ab induced in secondary response?
IgG
What are the 3 methods by which antibodies mediate humoral immunity?
Neutralization
Opsonization
Complement Activation
What are the levels of antibodies like just prior to birth?
Maximum levels of maternal IgG and the levels drop rapidly after birth and 6-9 months is a critical period
What are polyclonal antibodies?
Ab from multiple clones of B cells
What is intravenous immunoglobulin?
It is polyclonal antibodies pooled from many sources (10000 individuals) used to treat many types of diseases
What determines the isotope (class) of antibody?
The heavy chain
What are the classes of light chains?
Lambda and kappa
Each member of a light-chain isotype shares complete amino acid sequence identity of the carboxy terminal C region with all other members of that isotype.
What is the variable region of the antibody?
The combination of the variable region of the H chain and the variable region of the L chain make up the antigen binding site of an immunoglobulin.
