Immunoglobulin structure Flashcards
(45 cards)
IgG
Predominant antibody in the secondary immune response
IgA
Predominant antibody in external secretions
IgM
Predominant antibody in primary response
IgD
Found mainly on the surface of B cells
IgE
Involvement in allergic hypersensitivities
Common core structure of all antibodies
Two identical light chains and two identical heavy chains, where each light chain is attached to a heavy chain and the heavy chains are attached to each other
Immunoglobulin domain
Where all the chains, each of about 110 amino acids in length, all fold independently
Isotypes of light chain
Either kappa or lambda
N-terminal region of the heavy and light chains
Variable regions; the rest of them are all constant regions
Variable region
Combination of the heavy chain variable and light chain variable regions make up the antigen binding region
Constant region
Carries out other effector functions of the antibody (crossing the placenta, sites for attachment of Fc receptor, complement binding)
CDRs
Complementarity determining regions - three sites on the variable region above all else determine what will bind
How are the CDRs exposed?
When they fold, the portions of the CDR in the amino acid sequence stick out as projecting loops
How is IgM secreted?
In its pentameric form, with a molecular weight of 900,000 daltons
What joins the subunits of IgM?
The J chain
IgM is the primary antibody for antigen administered __
parenterally.
IgM is also the primary antibody elicited by __
T-independent antigen
How is IgM expressed on B cells?
As a monomer
Can IgM cross the placenta?
No
Approximate serum concentration of IgM
100 mg/dL
IgG is the antibody most characteristic for ___
secondary response
What is the difference in structure between IgG’s secreted and membrane form?
Nothing significant; both monomeric, both ~150,000 daltons
How does IgG recruit complement fixation?
Varies based on subclass
Can IgG cross the placenta?
Yes, due to presence of FcRn
