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48 Cards in this Set

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Immunoglobulin
= Ig = Antibody = Ab = gamma globulins
the ___________ of a B cell is due to the membrane bound Ig (part of the BCR complex)
Ag specificity
Abs can bind a variety of antigens
Proteins, polysaccarides, lipids, nucleic acids
Clonal selection and proliferation happens when
B cell recognizes it’s antigen and multiplies
Once a B cell is activated it differentiates into a memory cell or _______ which produces Ab with ____ antigenetic specificity.
plasma cell (effector cell);ONE
Overview of Ig functions
-Pathogen neutralization
-Complement (C’) fixation
-Antibody-dependent cellular cytotoxicity (ADCC)
-Opsonization
-Inflammation
agglutinatization
Ab can cause clumping together of cell
Precipitation
Ab can cause clumping together of small molecules
multiple myelomas
cancer of a B cell producing a monoclonal Ig
Heavy chain variation
mu,gamma,alpha,delta, or epsilon
light chain variations
kappa, lambda
antigen binding takes place on the ________ region of B cell Ag
variable region
Biological activity takes place on the ________ region of B cell Ag
Biological activity region
-where carbohydrate portions interact with complement
Ab structure
2 identical heavy chains and 2 identical light chains
-H-chains joined together by disulfide bonds in the hinge region
-L-chains joined to H chains by a disulfide bond in the CL region
-5 classes of heavy chains (isotypes: IgG, IgM, IgA, IgE, and IgD…a/k/a g, m, a, e, and d)
-2 types of light chains (k or l)
-Both H and L chains have intrachain disulfide bonds
-Ab binds in the N-terminal end where the VL and VH are joined
-F(ab) binds Ag
-Fc has biologic activity (C’ activation, ADCC)
F(ab)=
Fc =
-binds Ag
-has biologic activity (C’ activation, ADCC)
Ab has both ______ and _______ in its constant region and only _______ in its variable region
intrachain disulfide bonds, interchain disulfide bonds, intrachain disulfide bonds
intra chain immunoglobin fold
coded for by IG gene superfamily, connected by intrachain disulfide bond
IG subtypes with additional domains in constant region
mu, epsilon
________ of heavy chain determines function
glycosilation
Ig domain/fold
-The Ab molecule is made up of Ig domains
-Each domain is ~100-110a.a. long
-Contains an intrachain disulfide bond
-Molecules with this fold are members of the Ig gene superfamily
Ag binding domain
N-terminal region of variable region of heavy and light chain binds to Ag
Variability is concentrated in three regions:
Hypervariable regions
Called Complementarity determining regions (CDR): CDR1, CDR2, and CDR3
-CDR3 makes most of the contact with Ag
-Framework regions – areas of variable region that are less variable
Fab
antigen binding (VH:VL)
Fc
biological activity
5 H chain isotypes
m, g, d, a, and e
4 IgG
g1, g2, g3, and g4
2 IgA
a1 and a2
2 L chain types
k and l
Each Ab has 2 ______ H and 2 _______ L chains

In humans: __ of Ig have k, ___ have l
identical/ identical

60%/40%
five different IGs have different amounts of ____
glycosolation
Monomer-bivalent isotypes
IgG,IgE,IgD
dimer- multivalent isotype
IgA,
pentamer-multivalent isotype
IgM
J-chain (joining)
holds multimers together
Ig distribution in plasma
IgG (highest cuz involved in secondary immune response) and IgM; very low IgA, IgD and IgE
Ig distribution in tissue fluids
IgG, some IgM and some IgA monomers
Ig distribution in secretions
secretory IgA (dimers); small amounts of IgG in MALT
Ig distribution Fetus
passive IgG from mom (IgG1, IgG3, IgG4)
Ig distribution Beneath epithelium
IgE on mast cells
Ig distribution Brain
none unless damage to blood brain barrier
IgM
-pentameric when secreted from plasma cell
-10 Ag binding sites (highest valence of Igs)
-monomer on surface of mature B cell
-joined together by J-chain (15,000 mw)
-appears first during the primary immune response
best at C’ activation because need two Fc regions close together
-best agglutinating Ab – best at clumping together cells
IgG
-always a monomer
-2 Ag binding sites
-4 subclasses
-predominant Ig in blood and lymph
-Longest half life of isotypes (23 days vs. 2-5 days)
-appears in late primary and early secondary immune response
-can activate C’
-some subclasses cross the placenta
-Opsonin ( can bind to cells and act as a signal) and mediates ADCC( Ab dependant cellular cyttoxicity)
IgA
Secretory Ig
-monomer on surface of B cell
-dimer (can be tetramer) when in secretions
-J chain holds Ig together
-Secretory component (SC) present
-protective protein
-SC ~70,000 mw
-mucophilic – attaches to epithelial and traps Ags in mucous where lysozyme can help degrade
-Two subclasses
-Major Ig in the body (highest concentration) vs igg in blood
IgD
-monomer
-second receptor on B cell (after IgM)
-co-expressed on surface of B cell
-unknown function
-Initial B cell activation??
IgE
-reagin – binds to basophils and mast cells
-lowest concentration in the serum
-cleared from serum when binding to mast cells
-short half-life in blood but long on surface of mast cell
-when binds Ag, causes degranulation of mast cell = allergic reaction
-a/k/a Type I hypersensitivity (Immediate type hypersensitivity)
-protection against parasitic worms – causes acute inflammatory reaction
Isotypes
-classes of Igs (5 major classes in humans)
-determined by C-regions of the H-chain
-some describe light chain isotypes as well (k and l)
Allotypes
allelic forms of the same protein that can vary WITHIN A SPECIES (my Ab & your Ab)
usually 1-2 a.a. changes
Idiotypes
– due to the variable region of the Ig (differences in a.a. sequences due to variable binding to Ags) – determines Ag speficity
essentially a clonal marker for a given B cell