Lecture 6: MHC and Ag Presentation to T cells

Question 1

in order to activate T cells Antigens in host cells are broken up into ____ peptides (processed) and displayed by MHC molecules on their surface

Answer 1

linear

Question 2

T T cell antigen receptor (TCR) only recognizes ____ Antigens (peptides) bound to MHC molecules

Answer 2

linear peptides (processed)

Question 3

CD4 and CD8 attach to the _____ part of the MHC class II and MHC class I molecules, respectively

Answer 3

non-polymorphic (non-variant)

Question 4

is recognition of the peptide Ag by the TCR sufficient to activate the naive T cells

Answer 4

• No: co-stimulatory molecules are required together with co-receptors

Question 5

Th1 cells help ___ to get rid of intracellular microbes and help the development of ______ to kill virus-infected cells

Answer 5

• Macrophages, CTLs

Question 6

Th2 cells are mainly involved in helping _____ cells develop into ____ and ____

Answer 6

B cells develop into memory cells and plasma cells that produce antibodies

Question 7

The TCR is composed of _______ polypeptide chains

Answer 7

two (most are alpha and beta but some are are gamma and delta chains)

Question 8

The gamma/delta T cells have some of the characteristics of alpha/beta T cells, but have a

Answer 8

broader specificity for unconventional Ag such as HSPs and phospholipids

Question 9

The genes coding for TCR polypeptide chains are members of the

Answer 9

Ig super family

Question 10

The T cell receptor complex consists of the TCR, the alpha/beta or gamma/delta dimer, in association with

Answer 10

CD3

Question 11

CD3 is a signaling complex composed of ___, ____ and ____ chains

Answer 11

gamma, delta, and epsilon

Question 12

What are the three major class genes for Class I MHC

Answer 12

• HLA-A
• HLA-C
• HLA-B
• on chromosome 6

Question 13

What genes are responsible for MHC class II

Answer 13

• HLA-DR
• HLA-DQ
• HLA-DP
• on chromosome 6

Question 14

Class I MHC genes (HLA-A, HLA-B, and HLA-C) encode a polymorphic heavy chain which combines with _____ and is expressed on the surfaces of all nucleated cells

Answer 14

beta2-microglobulin

Question 15

Class II MHC genes (HLA-D) encode molecules (HLA-DP, HLA-DR, HLA-DQ) composed of two dissimilar ____________ (an alpha and beta chain), both of which contribute to the peptide-binding groove

Answer 15

polymorphic polypeptide chains

Question 16

MHC class I and class II are the peptide-binding domains of these molecules and bind peptides ranging from _____ and _____ amino acids residues, respectively

Answer 16

8-10 (MHC class I)

10-20 (MHC class II)

Question 17

Class I molecules are composed of a polymorphic alpha chain non-covalently attached to the ___________

Answer 17

non-polymorphic Beta₂-microglobulin (beta₂m)

Question 18

class II MHC molecules are composed of a polymorphic alpha chain non-covalently attached to a

Answer 18

polymorphic beta chain

Question 19

source of protein antigens for Class II MHC molecules

Answer 19

Endosomal/lysosomal proteins (mostly internalized from extracellular environment)

Question 20

Source of protein antigens for class I MHC molecules

Answer 20

Cytosolic proteins (mostly synthesized in the cell; may enter cytosol from phagosomes)

Question 21

Site of peptide loading for MHC class II

Answer 21

Specialized vesicles

Question 22

Site of peptide loading of MHC class I

Answer 22

Endoplasmic reticulum

Question 23

enzymes responsible for pepide generation for MHC class II

Answer 23

Endosomal and lysosomal proteases (e.g. cathepsins)

Question 24

Enzymes responsible for peptide generation for MHC class I

Answer 24

Cyoplasmic proteasome

Question 25

Molecules involved in transport of peptides and loading of MHC class II molceules

Answer 25

Invariant chain, DM

Question 26

Molecules involved in transport of peptide and loading of MHC class I molecules

Answer 26

TAP

Question 27

Peptide Ags that bind to class II MHC complexes are from the ____ pathway while peptide antigens for class I MHC are taken from the ____ pathway

Answer 27

• exogneous pathway (MHC class II)
• endogenous pathway (MHC class I)

Question 28

what is CLIP

Answer 28

• Class II-associated invariant chain peptide
  
  • it 24-amino acid remnant of the invariant chain that is placed in the peptide binding site. it is removed by HLA-DM (HLA-DM is a peptide exchanger that removes the CLIP and allows for the addition of other peptides)

Question 29

MHC class II (along with the invariant chain) is formed in the

Answer 29

ER

Question 30

What are the 3 major functions of HLA-DM

Answer 30

• HLA-DM causes the dissociation of CLIP from the peptide binding groove of MHC II
• HLA-DM stabilizes and prevents degradation of the empty MHC II
• HLA-DM facilitates the binding of Ag fragments to the open, stabilized binding groove

Question 31

How is CLIP formed

Answer 31

the degradation of the invariant chain by proteolytic enzymes in the endosome. This forms the 24 amino acid invariant chain known as CLIP

Question 32

What are immunodominant peptides

Answer 32

Applies to peptides presented by both class I and class II MHC molecules