Flashcards in 59-Antibody Structure and Function Deck (48)
1
antigen receptors
on surface of lymphocytes
B cell receptors
T cell receptors
many different receptors to recognize unlimited number of foreign Ags
clonically expressed-1 unique Ag receptor per lymphocyte clone
2
Surface BCR and soluble Ab molecules
identical except small transmembrane sequence on C terminal end
3
function of BCR
recognition of antigen
initiates signal transduction using CD79a/b to start intracellular signaling
4
CD79
needed for BCR to start intracellular signalling
5
structure of Ab
2 heavy chains
2 light chains
hinge region for torsion
disulfide bonds to hold molecules together
N linked carb chains linked to heavy chain for 3D structure and half life
6
variable region
heavy-VDJ
light-VJ
form antigen binding pocket, 2 identical pockets that bind identical antigens
7
constant region
no recombination, ensure structural integrity
H chain is for key effector functions
8
Fab region
Ag binding, 2 Fab regions=Fab2, bind 2 identical antigens
9
Fc region
below hinge region, heavy chain constant region
effector functions
10
Fab
cleave above hinge
11
Fc
cleave above hinge
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Fab2
cleave below hinge
13
hypervariability regions
3 regions in both heavy and light, "complementarity determining regions"
1 and 2 and encoded in DNA
3 is recombination of VDJ or VJ
14
CDR
complementarity determining regions, variability in heavy and light chains
proximal in tertiary structure and form Ag binding pocket
15
epitope
small segment of Ag bound by Ag binding pocket, non covalent interactions
16
what can TCRs recognize vs BCR/Ag
TCR-peptides, require MHC
BCR/Ag-lipid, carb, protein, nucleic acid, interact with epitopes on surface of pathogens, do not require MHC
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end product of B cell activation
cell that secretes Abs (soluble version of BCR) that recognize pathogen epitope and bind then recruite innate immunity to mediate destruction
18
Ab isotypes
defined by heavy chain constant region
5 isotopes encoded by loci
IgM, G, A, E, D
19
subclasses of Ab
IgG-4
IgA-2
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IgM structure
4 constant regions, no hinge
large and inflexible=only in blood
secreted as pentamer-10 binding sites
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antibody that is a pentamer
IgM
22
IgM functions
neutralization
agglutination
complement activation
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neutralization Abs
IgM, IgG, IgA
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agglutination Abs
IgM, IgG, IgA
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complement activation Abs
IgM, IgG
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IgG structure
3 constant regions with hinge
secreted as monomer-2 binding sites
most abundant
found in blood and tissues
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antibody that is a monomer
IgG, IgA in blood, IgE
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IgG functions
neutralization
agglutiniation
complement activation
opsonization/phagocytosis
Ab dependent cellular cytotoxicity
transplacental transfer
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opsonization/phagocytosis Abs
IgG, IgA
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Ab dependent cellular cytotoxicity Abs
IgG
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passive immunity to fetus through placenta Abs
IgG
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IgA structure
3 constant regions with hinge
monomer in blood
dimer in mucosal secretions
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antibody that is a dimer
IgA in mucosal secretions
34
IgA functions
neutralization
agglutination
opsonization/phagocytosis
immunity in breast milk
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immunity in breast milk Abs
IgA
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IgE structure
4 constant regions, no hinge region
monomer
37
IgE function
bound to mast cells with high affinity
mediate type 1 hypersensitivity reaction/ allergic reaction
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allergic reaction Abs
IgE
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IgD structure
3 constant regions with hinge, rarely secretes, used as BCR on naive B cells
40
no hinge
IgM, IgE
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agglutination
traps microbes in a complex
impair movement, attachment, replication, colony formation
IgM, G, A- lots of binding sites or hinge with torsion
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neutralization
prevent pathogens and toxins from binding to their host
IgM, G, A
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Complement activation-Classical pathway
Ab binding to Ag makes immune complex formation
allosteric change in Fc to bind C1q to start complement cascade, Use IgM, G
recruit C4 and 2, activation of C3 convertase
cleave C3, C3a inflammation, C3b opsinization
recruit and cleave C5, C5a inflammation
C5b recruits C6, 7, 8, 9 to form MAC, create channel and lyse
44
Opsonization
coating of pathogen with ligand recognized by phagocytic cells
IgG, IgA, C3b
45
Phagocytic cell receptors
Fc receptor bind antibodies
C3b receptor bind C3b
4 IgG Fc receptors, 1 IgA Fc receptor, 4 C3b receptor
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natural killer cells
IgG Fc receptors bind IgG Abs with their Fc tail
provide specifficity to NK cells to recognize and bind Ags on target cells
kill using proteolytic enzymes and inducing apoptosis
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maternal IgG
to fetus through circulation
can cause disease
hemolytic disease of newborns
IgG aBs against Rh blood group, give RhoGAM to Rh- moms
48