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How many signals are req for complete lymphocyte activation?
- two
- 1. interaction w/ specific antigen
- 2. interaction w/ co-stimulatory molecules
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Antibodies
B cell receptors for antigen; family of glycoproteins
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What are the two forms of antibodies?
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TCR
ONLY as membrane bound receptor, NOT secreted
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How are TCR diff from antibodies?
- TCR...
- 1. recognize Ags only
- 2. do not recog whole Ag
- 3. are only in mem bound form
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How many chains make up an Ig molecule? What bonds exist?
2 identical H chains, 2 identical L chains
- interchain disulfides: link peptide chains, i.e. H to L
- intrachain disulfides: link within peptide chains, i.e. w/in H chain
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IgD
delta heavy chain class
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IgG
gamma heavy chain class
gamma1-4
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IgE
epsilon heavy chain class
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IgA
alpha heavy chain class
alpha 1 or 2
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What are the light chain classes?
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Why is the hinge region sig in antibody structure?
it's proline rich characteristic allows the antibody arms to bend when binding to antigen
has interchain disulfides, protease sensitive
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Variable region domain
first 110 amino acids at AMINO TERMINAL of H and L chains (similarity to histones?)
least variable of all domains and allows specificity to antigens
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Constant region domain
- H chain: 3 or 4 domains
- L chain: 1 domain
consistent w/in a class
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L chain structure
each domain has 2 anti-parallel B-pleated sheets, linked by disulfide bond...makes B barrel! Loops that stick out into env form antigen binding sites
- "hydrophobic sandwich":
- bread=B sheets
- tuna=phobic parts of AA
- toothpick=intrachain disulfide
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CDRs
- complementarity determining regions or hypervariable regions: loops btw B pleated sheets
- -complementary to structure of antigen that binds
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Framework regions
conserved seq btw CDRs that correspond to B sheets and maintain integrity of Ig
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How many CDRs do H and L chains in humans have?
3 each...6 total
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What characteristics make a for a good fit?
low repulsion, high attraction
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What characteristics make for a poor fit?
low attraction, high repulsion
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What is affinity dep on?
chem features di gruppe coppie: H bonds, electrostatic, VdW, phobics
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Avidity
strength of interaction that involves antibodies binding to a single antigen by more than one binding site at the same time
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