Molecular Basis of Ag Recognition

Question 1

Which receptor can only recognize peptides presented by APC?

Answer 1

TCR

Question 2

What are the subunits of BCR?

Answer 2

IgAlpha and IgBeta

Question 3

What kind of antigen can be recognized by BCR?

Answer 3

lipids, proteins, carbs= Macromolecules

Question 4

Effector function of BCR

Answer 4

Fc region of Ab

Question 5

One one of the VLCL and VhCh alleles are expressed in single B cell what is this process called?

Answer 5

allelic exclusion; also governs expression of TCR

Question 6

How are variable regions of receptors determined?

Answer 6

rearrangement of DNA

Question 7

3 mechanisms of creating epitope-specific diversity?

Answer 7

Somatic recombination, mRNA splicing, and junctional diversity

Question 8

What initiates TCR or BCR rearrangement?

Answer 8

somatic recombination: includes deletion and reannealing

Question 9

name of genes that encode enzymes performing recombination of BCR and TCR during process of VDJ recombination

Answer 9

RAG 1 and RAG 2= recombination-activating genes 1 and 2

Question 10

during what stages are expression of RAG genes restricted to?

Answer 10

developmental stages of B and T lymphocytes

Question 11

How many gene segments does heavy chain have in chromosome 14?

Answer 11

4: VDJC; multiple copies of each so as to create variance

Question 12

BCR recombination sequence of events

Answer 12

1. D & J chosen; extra DNA deleted
2. V segment chosen; extra deleted
3. J chosen; DNA between VDJ and C deleted

Question 13

Name for producing rearrangement that does not contain stop codons

Answer 13

productive rearrangement

Question 14

Once productive rearrangement is confirmed what happens?

Answer 14

recombination of other gene is stopped

Question 15

If Vh rearrangement is productive then what occurs with B cell?

Answer 15

proliferates and “takes care” of VL

Question 16

how many tests of productive rearrangement occur?

Answer 16

2

Question 17

Where is junctional diversity generated?

Answer 17

points between joining genes

Question 18

Where are P nucleotides derived from?

Answer 18

asymmetric opening of hairpin loops

Question 19

How does junctional diversity result?

Answer 19

loss of nucleotides (exonucleases) and addition of N and P nucleotides

Question 20

What aids addition of N nucleotides?

Answer 20

Terminal deoxynucleotidyl transferase (TdT)

Question 21

TCR gene rearrangement

Answer 21

slide 20, 21

Question 22

Omenn syndrome results as a defect in what?

Answer 22

autosomal, missense mutation, partial rag1/2 activity

Question 23

What are the symptoms of Omenn syndrome?

Answer 23

lack of b cells, marked decrease in T cell count, severe immune deficiency with failure to thrive, diarrhea, red rush

Question 24

SCID results as a defect in what?

Answer 24

autosomal, null mutation in rag1/2 genes, no enzymatic activities

Question 25

Symptoms of SCID?

Answer 25

total lack of T and B cells, defect in both humoral and cell-mediated immunity

Question 26

Name for lack of reaction?

Answer 26

anergy

Question 27

T cell needs what 2 things for activation

Answer 27

MHC binding and co-stimulator binding

Question 28

binding of co-stimulator only has what effect on t cell?

Answer 28

none

Question 29

binding of MHC only has what effect on t cell?

Answer 29

anergy

Question 30

Activated APCs express high levels of?

Answer 30

MHCII and co-stimulatory molecules B7-1(CD 80) and B7-2(CD 86)

Question 31

What does protein B7 on APC interact with on T cells?

Answer 31

CD28

Question 32

Close contact between T cell and APC? what does it help ensure?

Answer 32

Immunological Synapse; ensures effector molecules (cytokines) are not affecting bystander cells

Question 33

3 pairs of molecules that interact in immunological synapse?

Answer 33

TCR/MHC-peptide Co-stimulator B7 and CD 28 Adhesion LFA-1/ICAM-1

Question 34

T Cell accessory molecules

Answer 34

slide 27

Question 35

Plasma cells are mostly found where?

Answer 35

in lymphoid organs

Question 36

B cells act as what to T cells?

Answer 36

Pro-APCs

Question 37

What is the coreceptor for BCR?

Answer 37

CD 19; can be used as specific marker of B cells

Question 38

What are the two mechanism of B cell activation:

Answer 38

Thymus independent and dependent

Question 39

TD Ags activate B cells with assistance of what?

Answer 39

T helper cells

Question 40

Steps of TD activation of B cells:

Answer 40

1. Antigen binding to BCR 2. Helper Th2 cell signal thru CD40 ligand and cytokines 3. B cell proliferates and differentiates

Question 41

How do BCRs bind to TI Ags?

Answer 41

repetitive epitopes on bacterium multiple BCRs bind= cross-linking= generates signal

Question 42

What transduces signal from BCR to inside cell?

Answer 42

IgAlpha and IgBeta

Question 43

What process must the signaling molecules undergo in TI Ags recognition

Answer 43

enzymes attached to the cytoplasmic portion of IgAlpha and IgBeta catalyze phosphorylation