Lecture 4, IG Structure Flashcards
What are the 5 Ig isotypes?
IgM, IgG, IgE, IgA, IgD
Describe the structure of an Ig
2 central heavy chains, each w/ a light chain attachment via di-S bonds.
- All 4 chains have a variable and constant domain
What’s another name for the hyper-variable regions of each chain?
CDR: complementarity-determining region
In the CDR, 3 hyper-variable regions combine to make a _______________.
Binding site
If treated w/a proteolytic enzyme, what would be the names of the resulting Ig fragments? *Which would tell you what class of Ig it is?
- Fab (ag-binding fragment)
- Fc (crystallizable fragment- constant region)
Fc would tell you Ig class
Which Ig’s aren’t only found in monomeric form, and what form are they found in?
What’s the name of their accessory protein, in each?
- Pentameric IgM
- Dimeric IgA
(both contain J chain as well)
If you see cell w/monomeric IgM on its surface, by definition it’s a _____________.
B cell
What’s an epitope?
About how many AA’s long do they span?
Antigenic determinant (small segment of ag where AB binds) - Usually 6-8 AAs long (so can be lots)
IgA in the mucosa is found as a ___________ but in the serum it’s found as a ___________.
- dimer
- monomer
What is the major AB of the body? Where is it mostly found?
IgA
- Mucosa
What’s the major AB of the blood?
IgG
What is the normal laboratory value of serum total protein?
What portion is Ig?
- 7 g/dL (wiki; but she says 100…)
- Ig: ~1/10th of the total protein found in blood (mostly IgG)
What’s the 1/2-life range of the Ig’s?
*Which typically has the longest 1/2-life?
~2-21 days
- IgG
Cross-linking of which Ig on mast cell leads to degranulation? (allergies)
IgE
What’s the name of the receptors that cells have to bind Ig’s?
Which part of the Ig do they bind?
Fc receptors (e.g. Fc-epsilon, Fc-gamma, etc) - Bind constant domain
By which 3 Methods do ABs mediate humoral immunity?
- Neutralization
- Opsonization (facilitates phagocytosis)
- Complement Activation (phagocytosis facilitated, sometimes w/lysis)
What must happen when an Ig binds an Fc in order for a response to occur?
Cross-linking
Prior to conception, fetus relies on what Ig from mom?
Fetus first starts to develop which of its own Ig’s?
What 2 come next, after birth?
- IgG
- IgM
- IgG, IgA
The total 1/2-life of AB’s to diseases like tetanus and measles is:
a. weeks
b. months
c. years
c. years
5-10 years for tetanus, 3,000 years for measles
AB from a clone of B cells is ___________. AB from multiple clones of B cells is ___________.
- Monoclonal
- Polyclonal
What is IVIG?
How is it made?
- Intravenous immunoglobulin: Polyclonal AB used to treat many immune deficiencies and inflammatory dz’s
- Made by taking serum from ~10K different people, isolate the serum, pool together (not known if it actually works)
Class-specific antigenic determinants are associated w/which part of the Ig molecule?
Constant region of heavy chain
How do you differentiate a T from B cell?
What about a specific type of B cell?
B cells have IgM on the surface.
- Could also look for kappa or lamba light chain to find a specific type of B cell?
What’s the major AB in secretions (saliva, tears, breast milk)?
Be specific
Mucosal IgA (dimeric)
