Antibodies
Terms
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- What is serum?
- The fluid phase that remains in clotted blood or plasma.
- What part of blood do antibodies reside?
- the Serum
- How heavy is IgG normally?
- 150,000 Da.
- Digestion of IgG with Papain produces:
- 3 fragments: 2 Fab, 1 Fc
- Digestion of IgG with Pepsin produces:
-
1 F(ab')2.
Fc is digested into pieces - What does mercaptoethanol reduction of the disulfide bonds in IgG show?
- That there are 2 heavy chains and 2 light chains.
- how much do the light and heavy chains of IgG weigh?
-
Heavy = 50 kDa
Light = 25 kDa - What is multiple myeloma?
- Unregulated proliferation of plasma cells that produce tons of homogenous antibody.
- What are bence-jones proteins?
- extra light chains secreted by myeloma cells in cancer patients.
- How many types of light chains are there? What are they?
- 2; Kappa and Lambda
- How many types of Heavy chains are there, what are they?
-
5;
IgG, IgM, IgD, IgA, IgE - Which isotypes have subclasses and how many?
-
IgG - 4 subclasses
IgA - 2 subclasses - What is the molecular unit of an antibody?
- an Immunoglobulin domain with an intramolecular disulfide bond.
- Characteristics of the Ig Domain:
-
100 residues
1 intramolecular disulfide bond
(60 residues per loop)
THE BUILDING BLOCK OF THE ANTIBODY - What type of structure are Ig domains?
- 2ndary structure = beta pleated sheets.
-
How many CDRs are in
-each variable domain
-each antibody - 3 per domain, so 6 per antibody.
- What does each immunoglob domain consist of?
- 2 B-sheets stabilized by a disulfide bond. (from her notes)
- What, structurally, are the variable regions of Ig domains?
- 3 Loops between beta sheets that show considerable variation in A.A. sequence.
- which contributes more to antigen binding usually, heavy or light variable regions?
- heavy
- 4 Functions of Immunoglobulins:
-
1. Precipitation/neutralization
2. Activation of complement
3. Activation of ADCC by NK cells
4. Opsonization for incr. phagocytosis - Which antibodies can exist as multimers?
- IgA and IgM
- Which is the most abundant Ab in serum?
- IgG
- Which antibodies activate complement?
- IgG, IgM
- Which Ab cross the placenta?
- IgG
- Which antibody is an opsonin?
- IgG
- which cell is IgM expressed on as a membrane molecule?
- mature B cells
- How does IgM exist in serum?
- Pentamer
- Which Abs have the J chain
- IgM, IgA
- Predominant Ab in mucosal secretions and breast milk:
- IgA
- Ab responsible for allergy:
- IgE
- Which are the first-secreted antibodies in an immune response?
- IgM
- which Ab are present on the mature B cell membrane?
- IgM, IgD
- 3 types of Antigenic Determinants on Ab:
-
1. Isotypic (what class of Ab it is)
2. Allotypic (diffnces btwn species)
3. Idiotypic (diffnces of Variable regions) - 2 Ab cross mother's epithelium to enter breast milk:
- IgM, IgA
- How/when is Secretory IgA formed?
-
When: during transport through mucous membrane epithelial cells.
How: Dimer of IgA binds a "poly-Ig receptor" on basolateral membrane; epithelial cell endocytoses it; Transport to endothelial surface; cleavage of IgA with secretory component