define an antibody
a protein that is produced in response to a fogey molecule (an antibody), and has the property of binding specifically to that antigen
When an antigen binds, what happens to the Fc part of the immunoglobulin?
changed conformation and can perform effector function such as activating complements
Around how many interactions are there between an antigen and an antibody?
20
Where are the hyper variable regions and what do they do?
located at loops at the ends of proteins/V domains
they are the areas that interact with the antigen
Why is avidity a better measure of binding capacity than affinity?
- affinity is between a single antigen and antibody binding site
- but antibodies have a minimum of 2 binding sites
- avidity considers multiple interactions between an antibody with multiple binding sites and antigens with multiple epitopes
How do different classes of antibodies differ?
in their constant regions of their heavy chains
Ig G
- 4 subclasses that differ mainly in the hinge region and effector function domains
- passes across the placenta
- major activator of complements (classical pathways)
Ig A
- monomer in blood, dimer when secreted
- protects mucosal surfaces
DIMER FORM (secretory) - joined by J chain
- has a secretary component, that helps to protect the molecule from being degraded by the enzymes found on the mucosal surfaces
In secretory IgA, how are the immunoglobulins joined together?
J chain
Where does the secretory component of secretory IgA come from?
derived form the poly-Ig receptor
IgM
- pentameric
- all joined by a J chain and held together by disulphide bonds
- mainly confined to the blood
- first Ig produced after exposure to antigen
- low affinity, high avidity- activates complement
IgD
- low serum concentrations
- involved in B cell development and activation
IgE
- produced in response to parasitic infection and allergic disease
- binds to high affinity Fc receptors of mast cells and basophils
- triggers mast cell activation and histamine release
What is the first immunoglobulin type to be produced after exposure to antigen?
IgM
Antibodies are which type of immunoglobulin?
gamma (IgG)
Which is the main immunoglobulin in the extracellular fluid?
IgG
Which immunoglobulin is secretory?
Dimeric IgA
