T Cell Receptor

Question 1

What is the function of MHC?

Answer 1

Monitor IC environments by presenting short peptide fragments on surface of cell to T cell to either signal response against foreign protein

Question 2

How do you get diversity of TCR? (5)

Answer 2

1. recombination of VDJ segments
2. recombination of different number of gene segments
3. imprecise joining by RAG
4. P and N nucleotide addition by TdT
5. Assembly of different combos of rearranged TCR chains (alpha/beta or delta/gamma)

Question 3

Does TCR have affinity maturation?

Answer 3

No, because it doesn’t have somatic hypermutation

Question 4

What do cytosolic peptides bind to? What are they presented to? What is the effect on presenting cell?

Answer 4

-binds MHC class I, present to CD8, and causes cell death

Question 5

What do intravesciular pathogens bind to? What are they presented to? What is the effect on presenting cell?

Answer 5

-binds MHC class II, presents to CD4, and activates the APC to kill intravesicular bacteria and parasites

Question 6

What do extracellular pathogens and toxins bind to? What are they presented to? What is the effect on presenting cell?

Answer 6

-binds MHC class II, presents to CD4, activates B cells to secrete IG to eliminate EC pathogen

Question 7

Is this affinity of TCR for Ag weak or strong compared to Ab?

Answer 7

weak

Question 8

What region of the MHC protein do CD4 and CD8 recognize?

Answer 8

constant region, can interact with any MHC class II or class I protein respectively

Question 9

What does gamma-delta TCR recognize?

Answer 9

3D shape of MHC molecule or Ag, not dependent on peptide held by MHC

Question 10

How do superantigens work?

Answer 10

• recognizes outside constant regions of TCR and MHC to bind both in a nonspecific manner
• increases frequency of T cell response from 1 in 10^4 to 10^5 to 1 in 4 to 20 to get huge cytokine release

Question 11

Does superantigen have any specificity?

Answer 11

-has specificity for certain VB segments, increases susceptibility for certain people

Question 12

What HLA types make up class I MHC? class II?

Answer 12

for class I, HLA-A, HLA-B, HLA-C (homodimer)
for class II, HLA-D (heterodimer)

Question 13

Where does the diversity come from for class I MHC? Class II?

Answer 13

for class I, diversity comes from number of alleles (6) since it's a homodimer
for class II, diversity comes from heterodimer arrangments

Question 14

Which class of MHC is expressed on all nucleated cells?

Answer 14

MHC class I

Question 15

What class of MHC is expressed on APCs?

Answer 15

MHC class II to allow interact with CD4 T cells so it can secrete cytokines to help B cells

Question 16

What is the structure of MHC class I? Which subunits make up the binding groove?

Answer 16

• alpha 1, 2, 3 (transmembrane), beta 2

- alpha 1 and 2 make up binding groove

Question 17

What is the structure of MHC class II? Which subunits make up the binding groove?

Answer 17

• alpha 1, 2 (transmembrane), beta 1, 2 (transmembrane)

- alpha 1 and beta 1 make up the binding groove

Question 18

Which MHC class has a closed off binding groove that fits smaller peptides only?

Answer 18

class I

Question 19

Which class of MHC do extracellular pathogens present from?

Answer 19

class II

Question 20

What is the processing pathway for IC pathogens?

Answer 20

• pathogen in cytosol degraded in proteasome to peptides

- transported into ER where they bind MHC previously held by chaperones, and are exported to cell surface