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80 Cards in this Set

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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?
Heavy?
25000

50000
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.
CDR
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
papain
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?

Carboxy terminal?
Variable

Constant
How many basic amino acid sequences of constant region of light chains?
2.
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?
4
How many basic amino acid sequences encode the constant regions of heavy chains?

What's another name for them?
5:
nu, delta, gamma, epsilon, alpha

ISOTYPE
how many amino acids are delta, gamma, and alpha?

epsilon and nu?
330

440
u is what letter Ig?
IgM
delta
D
gamma
G
epsilon
E
alpha
A
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
subtle amino acid differences within a species.

e.g., mom develops antibody to fetus because fetus has paternal alleles.
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.
hybridoma
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?
100

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
plasmacytomas
clones of malignant plasma cells
isotype
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.
opsonization
promotion of phagocytosis of antigens by macrophages and neutrophils
cells that have FcR
macrophages and neutrophils have Fc receptors
Antibody-Mediated Effector Functions
-opsonization
-complement activation
-ADCC
-Transcytosis
effector functions of antibodies according to pinfen
-precipitation/neutralization
-opsonization
-complement activation
-ADCC
transcytosis
movement of Ab across epithelial layer
Which antibody subclass undergoes transcytosis?
IgA
what minor Ig subclass undergoes transcytosis
IgM
How Ab gets to mucosal surfaces of tracts, and to breast milk:
transcytosis
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?
Structure?
IgG

-Monomer
-Crosses placenta
-Mediates opsonization
-Activates Complement
First Ig class to be secreted after primary antigen challenge:

-How is it expressed?
IgM

-mIgM = monomer; sIgM = pentamer (which is secreted by plasma cells)

Function: activates Complement, minor role in mucosal secretions (with IgA)
Predominant Ig in secretions:

structure:

in what secretions?
IgA

monomer or multimer.

Breast milk, saliva, GI, GU, resp tracts
Structure of IgA in
-serum

-secretions
monomer or other


dimer or tetramer
Ab responsible for allergy:

cells that express receptor for its Fc:

mechanism:
IgE

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?
IgD
3 types of epitopes on antibodies:
-isotypic
-idiotypic
-allotypic
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.
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.
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.
some members:

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.
chimeras
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..