Immuno Antibodies Flashcards
The strength of the binding between a single site of an antibody and an epitope of an antigen is called
Affinity
What part gives antibodies flexibility and why is it important?
Hinge region, it allows the antibody to bind multivalently to more than one binding site (each antibody has 2 binding sites).
What is avidity?
The strength of binding of an antibody and it includes binding to multiple epitopes or binding sites. (IgM has highest avidity)
What is the structure of an antibody?
2 heavy chains and 2 light chains. They are attached by disulfide bonds. each has a constant region and a variable region. The constant region of the heavy chains binds to cell receptors and C1q. At the edge of the variable regions of each heavy chain there are 3 hyper-variable regions or CDRs that vary between antibodies and increases affinity to the antigen.
What are the 5 Ig classes and the polymerization?
IgM pentamer
IgA dimer
IgG monomer
IgE monomer
IgD monomer
How do the Ig isotypes differ?
they differ by the type of heavy chain.
Each has a different location.
Each appear at a different time in the immune response.
What is the most abundant Ig isotype in serum?
IgG
How do B-cells develop into a cells that each produces antibodies with the different specificities?
As B-cells mature, gene-splicing reactions give each cell a unique specificity.
How are B cells activated?
A pure antigen is presented to the B-cell and is internalized and displayed on MHC 2, helper T cells with the same antigen bind to the B-cell and activate the B-cell. T-cells produce cytokines to induce B-cell proliferation.
How do memory cells work?
They are differentiated B-cells, when stimulated by an exposure of a prior antigen, they will turn into plasma cells secreting IgM initially.
Do plasma cells have BCRs (B-cell receptores)
No
What is a primary response and how long does it take?
initial contact with a new antigen evokes a response that takes 1 week for the B-cells to start producing antibodies.
How does serum antibody composition change over time with infection?
At baseline, only innate defense Ig are found. After the primary response of 1 week. mainly IgMs are produced, increasing concentration in serum, over the span of 3 weeks, concentration increases and IgMs are gradually replaced with IgGs before concentration falling off.
What is the difference between a primary and a secondary response?
Shorter lag phase.
Rate of Ig concentration increase is higher.
Higher maximum threshold.
Predominantly IgGs
Describe class switching over time.
An initial secretion of IgMs.
T-cell cytokines induce class switching to provide a variety of antibodies (IgG, IgA, IgE).
It is accomplished by genetic rearrangement of the constant region (variable unchanged, so same specificity).
The ability of antibodies in any individual to specifically bind a large number of different antigens is a reflection of antibody:
Diversity (each antibody is still specific to 1 antigen, but there are many different antibodies)
What are the sections of the antibody that are being edited in immune cells when forming antibodies with different specificities?
Variable regions of the light and heavy chains. (by genetic recombination and nucleotide addition)
What is affinity maturation?
Mutations in B-cells that generate new variable regions can increase the affinity to a specific antigen, thus working more effectively.
What are the functions of antibodies?
Activating complement system.
Opsonization.
Neutralization of toxins.
Agglutination.
What are some functions that serum IgMs excel at?
Agglutination: they can bind many antigens thus have the ability to bundle up pathogens.
Complement activation: IgMs bind many antigens, thereby activating the classical complement pathway.
What class of antibodies can cross the placental barrier?
IgG
What is the most abundant immunoglobulin in the body?
IgG
What are some characteristics of IgG?
Most abundant
long-lived antibody response
Crosses placental barrier
What are some characteristics of IgA?
Works in local immunity, protecting epithelial surfaces.
Found as a dimer.
Combines with secretory piece protein at epithelial surfaces, forming secretory IgA which prevents antigen-carrying particles from binding to epithelial cells.
