Glossary of Chpt 4
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- y-globulin fraction
- fraction of serum that contains antibodies, aka, immunoglobulins
- What are Antibodies Heterodimers of?
- 4 chains; 2 light, 2 heavy.
This is the common structure of all antibodies.
- How many polypeptides in light chains?
- How are light chains bound to heavy?
- -Disulfide bonds
Noncovalent linkages - salt , hydrogen, hydrophobic bonds.
- V Regions
- VL=light VH=heavy
The first 110 amino acids of the north amino end of chains;
Highly variable sequence.
-Responsible for the variability in antigen specificity between Abs.
- Complementarity Determining Regions
On LIGHT and HEAVY chains
Antigen binding site on an Ab
- C region
- the constant region of antibodies.
-site of carbohydrate attachment
- digests antibody to produce 3 fragments.
2 identical: FAB - fragment, Ag binding
1 other: crystallizes during cold storage, so Fc
- Fc fragment
- the fragment produced by papain digestion that does not bind antigen and cyrstallizes
- multiple myeloma
- cancer of Ab-producing plasma cells
-normal plasma cells are endstage.
-clones in mmlma are unregulated- no stimulus, just proliferate.
- myeloma protein
- antibody from a myeloma patient - undistinguishable from normal Ab
- Bence-Jones proteins
- excess light chains excreted into urine by mmlma patinets
- amino terminal end: what type of region?
- How many basic amino acid sequences of constant region of light chains?
Kappa and Lambda
- How many types of light chain constant regions are expressed in one Ab molecule?
- only 1. either lamda or kappa
- how many subtypes of Lambda in humans?
- How many basic amino acid sequences encode the constant regions of heavy chains?
What's another name for them?
nu, delta, gamma, epsilon, alpha
- how many amino acids are delta, gamma, and alpha?
epsilon and nu?
- u is what letter Ig?
- Immunoglobin Domains
- 2 types: Variable (Vl/Vh)
and Constant (Cl/Ch)
Light chains: 1 Vl, 1 Cl
Heavy chains: 1 Vh, 3 or 4 Ch
- Immunoglobulin fold
- characteristic fold of Ig domains; each domain contains 110 a.a., folded into antiparallel beta pleated sheets. Ig fold is a sandwich of the two sheets, with intramolecular disulfide bond holding them together. the cheese is hydrogen bonding.
- hypervariable regions
- highly variable in their amino acid primary structure - antigen binding sites of the antibodies - aka, complementarity determining regions
- framework regions
- the regions on variable domains (Vl/Vh) that are not highly variable (like CDR) but are more constant. the framework supporting the six CDR folds in the Fab fragment
- Purpose of Ch1 and C-light regions on Ab
- -to extend Fab arms of Ab molecule
-to increase overall diversity of CDR regions by increasing stability (gives a disulfide bond between H and L chains!)
- What type of Ig has the hinge region?
- IgG, IgD, IgA.
-makes the Fab arms more flexible.
- Since IgE and IgM don't have a hinge region, how do they make up for it?
- by having an extra Ch domain.
- What's different in mIg and sIg?
- the tail; carboxy terminal end is designed to fit the need.
hydrophilic - secreted
hydrophobic - memb. bound
- immature B cell expresses what Ig?
- only IgM.
- what is ADCC?
- Antibody dependent cell-mediated cytotoxicity. Fc region on Ab binds to Fc receptor on NK cells; the Ab actually acts as a receptor on the pathogenic cell, so NK cells can bind and kill the pathogenic cell.
- allotypic determinants
- alleles that encode subtle a.a. differences so that even if two strains have IgG, you can't infuse from one mouse to the other because allotypic determinants will be foreign.
- idiotypic determinants
- the variable regions on H and L chains actually act as antigens themselves.
individual determinents are idiotopes
idiotype = sum of idiotopes, which are spread out all over the variable region.
- polyclonal antibody response
- antigens that stimulate response have various epitopes, so bind/stimulate variety of Bcells, to proliferate and secrete a heterogenous variety of antibodies.
- monoclonal antibody response
- stimulation and production of only one type of clone of antibody and bcells. specific for one single epitope.
- multiple myeloma cell fused to activated, antibody-producing b cell. has immortal life but produces monoclonal antibody. limitless supply!
- which two Ig classes have subsets, and what are they?
- IgG - g1, g2, g3, g4
IgA - a1, a2
- how many amino acids in Ig domain?
How many disulfide bonds, what type?
2 disulfide bonds, intramolecular
- what is the building block of an Ab?
- immunoglobulin domain
- what is the J chain for?
- joining together 2 IgA molecules into a dimer. OR, joining 5 IgM molecules into a pentamer.
- which Ig's are MONOMERS
- IgG, IgE, IgD
- papain digestion gives
pepsin digestion gives
Mercaptoethanol reduction gives
- 2 Fab and 1 Fc fragment
1 fragment = F(ab')2
2 H and 2 L chains
- clones of malignant plasma cells
- name for each of the 5 different Heavy chains
- definition of variability
- # of different amino acids at a given position/frequency of most common amino acid at given position
- Where are hypervariable regions?
Why called that?
- in the loop regions joining b-sheets in domains of vheavy and vlight chains.
Maximum variation in which amino acids occupy these sites is seen here.
- purpose of hinge region in which Abs
- IgG, IgD, IgA
Gives flexibility to segments
- Which mIg are expressed at which developmental stages?
- Early immature B cell: mIgM only
Later immature B cell: IgM/ mIgD - before antigen activation
Memory B cell: mIgM, mIgG, mIgA, mIgE.
- promotion of phagocytosis of antigens by macrophages and neutrophils
- cells that have FcR
- macrophages and neutrophils have Fc receptors
- Antibody-Mediated Effector Functions
- effector functions of antibodies according to pinfen
- movement of Ab across epithelial layer
- Which antibody subclass undergoes transcytosis?
- what minor Ig subclass undergoes transcytosis
- How Ab gets to mucosal surfaces of tracts, and to breast milk:
- What Ig subclass crosses the placenta from Mother to Fetus
- IgG - most subclasses of it too (4)
- what type of immunization is transfer of Ig (which one?) from mother to fetus?
- Passive - IgG
- Most abundant Ig in Serum:
What does it do?
- First Ig class to be secreted after primary antigen challenge:
-How is it expressed?
-mIgM = monomer; sIgM = pentamer (which is secreted by plasma cells)
Function: activates Complement, minor role in mucosal secretions (with IgA)
- Predominant Ig in secretions:
in what secretions?
monomer or multimer.
Breast milk, saliva, GI, GU, resp tracts
- Structure of IgA in
- monomer or other
dimer or tetramer
- Ab responsible for allergy:
cells that express receptor for its Fc:
basophils and mast cells express FcR
crosslinking of IgE by binding to multiple Antigens AND mast cells. Mast cells/basophils release histamine, inflammatory compounds (degranulation).
- Which Ig has no real function, but is the major membrane-bound Ig with IgM?
- 3 types of epitopes on antibodies:
- isotypic determinants
- CONSTANT REGION epitopes
-define each heavy-chain class/subclass
-define each light chain type/subtype
- isotypic determinants are foreign for whom?
- same/non-foreign within a species
foreign when injected into another species.
- significance of idiotype
- -antibody variable regions have distinct primary structure; this is recognized as foreign when injected in large amounts (monoclonal ab). then the recipient can raise anti-idiotypic antibodies.
- why secretory IgA, not just IgA?
- Secretory IgA is formed when IgA binds to polyIg receptor on basolateral membrane; a vesicle takes the complex across the epithelial cells and is released as Secretory IgA inside the lumen, to fight pathogens.
- immunoglobulin superfamily
- membrane proteins of which their genes were derived from a common primordial gene encoding the basic immunoglobulin fold domain structure.
TcR, MHCI and II, etc.
- common membrane feature of immunoglobulin superfamily:
- carboxy-terminal end of molecule is anchored in cell membrane
- making immunotoxins
- toxins normally have binding chains and thier inhibitory toxin chain. replace the binding chains with monoclonal antibody specific for cancer cell or whatever. it binds, delivers the toxin to the cell, it is released in the cytosol and does its toxic thing.
- what does differential processing do?
- determines whether Ig will be membranous or secreted. poly A signaling sequences point to places for excising rna. S is before M1 and M2. if cut is between S and M1, it will be secreted; if after m2, then membranous.
- How can IgM and IgD be expressed at the same time?
- there is no switch site for circular excision between the two gene segments. therefore they can both be transcribed/translated at the same time.
- molecular hybrids that link nucleotide sequences coding nonantibody proteins with sequences encoding antibody variable regions specific for ag.
- humanized antibody
- contains promotor, leader, and variable regions from mouse antibody gene, constant region exons from human.
less immunogenic when administ. to humans.
- chimeric immunotoxins
- Fc region is replaced with a toxin, so Fcreceptors on self cells don't recognize the antibody, but the variable region does, so the target cell is toxicated! like tumor cells..
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