5-Antigen Recognition by T cells

Question 1

What type of Ag can T-cell Receptors (TCR’s) bind to?

Answer 1

Peptides

Question 2

When does TCR rearrangement occur?

Answer 2

Only during development

Question 3

Why is rearrangement different in TCR’s than BCR’s (Ab’s)?

Answer 3

Because Ab’s can rearrange to form a tighter bond with an Ag whereas TCR’s cannot rearrange after development

Question 4

What are the RAG genes?

Answer 4

They are recombination activating genes that rearrange genes of Ig’s and TCR’s.

Question 5

What disease occurs if there is a defect in the RAG genes?

Answer 5

SCID (severe combined immunodeficiency disease)

Question 6

What is the clinical manifestations of SCID?

Answer 6

No B or T cell production leads to infections because there is no adaptive immune system.

Question 7

What is the cause of Omenn syndrome?

Answer 7

It’s a missense mutation in the RAG gene

Question 8

What ara the clinical manifestations of Omenn syndrome?

Answer 8

Quickly die, chronic inflammation and a bright red rash on the face and shoulders.

Question 9

What are the components of the TCR complex?

Answer 9

The T cell receptor (α and β subunits) and 3 proteins from the CD3 family

Question 10

What are the 2 functions of the CD3’s?

Answer 10

They move the TCR to the cell surface and help signal the inside of the cell when an Ag is bound to the TCR

Question 11

What % of the TCR population is the γδ type?

Answer 11

Only 1-5%

Question 12

Where are the γδ TCR’s located?

Answer 12

On epithelial tissue to defend the epithelium, like gut epithelium

Question 13

What is the other name of the CD4 cells?

Answer 13

Helper T cells

Question 14

What are the functions of the helper T cells?

Answer 14

Help other cells (like macrophages) respond to an infection, stimulation of B cells to produce Ab’s, secrete cytokines, and responds to MHC-II molecules

Question 15

What is the other name of the CD8 cells?

Answer 15

Cytotoxic T cells

Question 16

What are the functions of the Cytotoxic T cells?

Answer 16

Kill cells that have been infected with a virus or intracellular agent, and responds to MHC-I molecules

Question 17

What are the general functions of the TH1 cells?

Answer 17

They enter the blood to seek out infections and secrete IFN-γ and activate macrophages.

Question 18

What are the general functions of the TH2 cells?

Answer 18

They remain in the secondary lymphatic tissues to drive the proliferation and differentiation of B cells

Question 19

What type of organisms get presented by an MHC-I molecule to a Tc cell?

Answer 19

intracellular organisms

Question 20

What type of organisms get presented by an MHC-II molecule to a Th cell?

Answer 20

extracellular organisms

Question 21

What is the structure of the MHC-I molecule?

Answer 21

1 large 3-part alpha subunit coded by the MHC gene and a small beta2 subunit not coded by the MHC gene

Question 22

What is the structure of the MHC-II molecule?

Answer 22

has 2 equal sized subunits, which are both coded by the MHC gene.

Question 23

Why do people say that the TCR has degenerate binding when compared to the BCR?

Answer 23

Because the TCR can bind to a wide rage of peptide sequences whereas the BCR’s are very specific.

Question 24

Why do the MHC-I molecules bind smaller peptides than MHC-II?

Answer 24

Because the binding pocket on the MHC-I molecule is smaller due to the weird 3 alpha chain thing.

Question 25

When the proteins are taken up by a cell, what is that vesicle called?

Answer 25

Proteasome

Question 26

How do the small peptides of the immunoproteasome get pumped into the ER?

Answer 26

TAP 1 and 2 (Transporter associated with Antigen Processing)

Question 27

After the proteins are pumped in by TAP, what is then pumped into the ER?

Answer 27

the MHC-I alpha and beta subunits

Question 28

What helps fold the alphas and beta chains of the MHC-I molecule in the ER?

Answer 28

Calnexin

Question 29

After the MHC-I is folded to its correct form, what happens with the MHC molcule and the proteins from the immunoproteasome?

Answer 29

They bind and then leave in leave in a vesicle to the membrane

Question 30

What is bound to MHC-I molecules in the absence of an infection?

Answer 30

self-peptides

Question 31

What is the cause of the Bare Lymphocyte syndrome?

Answer 31

The TAP proteins don't work so the peptides from the immunoproteasome cannot enter the ER

Question 32

What type of infections do Bare Lymphocyte syndrome patients suffer from?

Answer 32

Intracellular infections like viruses because they have 1% of the normal MHC-I levels

Question 33

What happens to the proteins of the extracellular pathogens when they enter the APC cell?

Answer 33

They are pwned by lysosomes.

Question 34

What fuses with the phagosomes when the bacterial proteins are all broken up in an APC?

Answer 34

Vesicles from the golgi containing MHC-II

Question 35

What is the function of the invariant chain?

Answer 35

It binds to the MHC-II binding site so that it doesnt bind to the normal proteins in the ER

Question 36

When the MHC II compartment is being transported to the phagosome, what happens to the invariant chain?

Answer 36

It is cleaved to become CLIP, which are small chunks of the invariant chain.

Question 37

What is the function of the HLA-DM?

Answer 37

It removes CLIP from the MHC II compartment and allows the target peptide to bind to the MHC-II molecule.

Question 38

Which has more allotypes, MHC-I or MHC-II?

Answer 38

MHC-I

Question 39

What is an allele?

Answer 39

Different form of a gene

Question 40

What is an allotype?

Answer 40

encoded protein from an allele

Question 41

What is an isoform?

Answer 41

any particular form of an MHC protein

Question 42

Why is the highly polymorphic nature of the MHC important?

Answer 42

It allows it to be effective and adaptible to a large range of pathogens.