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HDM > Lecture #4: Adaptive Ag Recognition > Flashcards

Lecture #4: Adaptive Ag Recognition Flashcards

1
Q

Fab/Fc Fragments

A

Fab = fragment Ag binding

Fc = fragment crystallized)

Both have effector functions

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2
Q

Where are most Abs found in the globulins?

A

Third, slowest migrating group i.e. “gamma” globulins

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3
Q

Effector Properties of Abs

A

Immunomodulation

Reduce host damage from inflammation

Organized T cell response

Opsonization

Activate complement system

Toxin neutralization

Direct antibacterial activity

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4
Q

Papain

A

Cleaves IgG at the heavy chain into two Fab fragments and complement: Fc receptors binding the Fc fragment

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5
Q

Proteolysis of IgG by Pepsin

A

Generates a single bivalent Ag-binding fragment F(ab’)2

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6
Q

Five classes of Abs

A

IgM, IgD, IgG, IgE, IgA

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7
Q

Two different kinds of light chains:

A

K and delta

Ab unit can only have one or the other at one time

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8
Q

Ig Superfamily Proteins

A 
T cell receptor
MHC Molecules
CD4 coreceptor of T cells
CD28
ICAM-1
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9
Q

Properties of Secreted IgG

A

Ag-binding sites formed by juxtaposition of VL and Vh domains

Heavy chains C regions end in tail pieces

The locations of complement-Fc RC-binding sites within the heavy chain constant regions are approximation

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10
Q

Properties of Membrane-bound IgM on B cell

A

One more CH4 domain than IgG

Has C terminal transmembrane and cytoplasmic portions that anchor in the plasma membrane

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11
Q

Locations of Ab Hinges

A

Between Ch1 and Ch2 domains

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12
Q

Structure/function/concentration of IgA

A

Mainly dimer, also monomer, trimer

Mucosal immunity

3.5mg/ml

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13
Q

Structure/function/concentration of IgD

A

Monomer

Naive B cell Ag Rc

Trace

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14
Q

Structure/function/concentration of IgE

A

Monomer

0.05mg/ml

Defense against helminthic parasites, immediate hypersensitivity

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15
Q

Structure/function/concentration of IgG

A

Monomer

13.5mg/ml

Opsonization, complement, Ab dependent cell mediated cytotoxicity, neonatal immunity, feedback inhibition of B cells

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16
Q

Structure/function/concentration of IgM

A

Pentamer

1.5mg/ml

Naive B cell Ag receptor, complement activation

17
Q

Ab Affinity

A

Lower in the primary response but higher in the memory response to Ags, they have a higher binding constant and are less likely to dissociate

18
Q

Valence of an Ab

A

Max number of antigenic determinants with which it can react

Ex: IgG has two Fab regions that can two Ags, so it has a valence of 2

Increases the affinity

19
Q

Avidity

A

Overall strength of an Ab-Ag complex

Dependent on:

  • affinity of Ab for epitope
  • Valence of both Ab and Ag
20
Q

Steps in production of monoclonal Ab

A

Splenocytes from mouse immunized with known Ag isolated

Cells fused to myeloma cells with polyethylene glycol (myeloma cells don’t secrete own Ig)

Cells placed in HAT (hypoxanthine, aminopterin, thymidine) only they survive because they lack HGPRT

21
Q

Aminopetrin

A

Blocks de novo purine synthesis during production of monoclonal Ab

22
Q

Basic Structure of TCRs

A

Membrane bound, heterotrimeric with A and B chain

Each chain has one variable and one constant region

In V region, there are 3 complentarity-determining regions (CDR) each corresponding to a loop in V domain

23
Q

Structure of the TCR Complex

A

A/B TCR non-covalently linked to the CD3 and zeta proteins which are the signal transducing subunits

Association mediated by charged residues in transmembrane regions

A/B chains carboxyl cyto tails 5-12 aa long

24
Q

CD4 vs CD8 Co Receptor Structures

A

CD4: 4 extracellular Ig-like domains, hydrophobic TM region, basic cyto tail 38 aa long

CD8:
made of CD8a/b which have = Single extracellular Ig domain, hydrophobic TM region, basic cyto tail 25 aa long

25
Q

Genes for Human Ig’s

A

H-chain = Chrom 14 (heavy)

K-chain = chrom 2 (light)

Delta chain = chrom 22 (light)

26
Q

Allelic Exclusion

A

Inherit maternal and paternal alleles for L and H chains but only express one

Same for TCRs

Allotypes expressed equally

27
Q

RAG1 and RAG2

A

Recombination Activating Genes

Initiate VDJ recombo via DS breaks in DNA

Resolved by nonhomolgous end-joining (NHEJ)

28
Q

3 Mechanisms of Ag Rc Diversity

A

Somatic Recombination

MRNA splicing

Junctions diversity

29
Q

Terminal Deoxynucleotidyl Transferase (TdT)

A

Adds or removes N nucleotides to the exposed ends of the V, D or J genes before they are reunited

30
Q

Junctional Diversity

A

Results from loss of nucleotides via exonucleases and addition of N and P nucleotides- generated from asymmetric opening of hairpin loops

Get 10^11 Ig and 10^16 TCR

31
Q

Pre-BCRs Contain:

A

Ig mu heavy chain

32
Q

Pre-TCRs contain:

A

TCR B chain

HDM (7 decks)

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