Immuno Assignment #5

Question 1

What is the role of MHC class I molecules??

Answer 1

Alert CD8+ T cells that the cell is infected

Question 2

All nucleated cells express class I or class II MHC?

Answer 2

Class I MHC

Question 3

What is the nomenclature for class I MHC?

Answer 3

HLA-A, HLA-B, and HLA-C

Question 4

Class I MHC express codominant pattern why is this advantageous?

Answer 4

because each cell now has the potential to express six different class I HLA (MHC) molecules

Question 5

Class I MHC are polymorphic why is this advantageous?

Answer 5

allows several alleles in the population (good from an evolutionary stance)

Question 6

What are the mouse isotopes for MHC class I

Answer 6

H2-K, H2-D, H2-L

Question 7

Class I MHC are present on all ________ cells, while professional _____ cells express class II MHC and class I MHC

Answer 7

nucleated

antigen presenting

Question 8

What is the general structure of HLA-class I molecules?

Answer 8

transmembrane polymorphic polypeptide heavy chain non covalently associated with a smaller non polymorphic chain (B2- micro globulin)

Question 9

What are the number of different HLA-class I molecules that will be expressed on cells if the parents are genetically unrelated?

Answer 9

six different stable heterodimers possible

Question 10

What HLA allele is expressed in most patients with Ankylosing Spondylitis?

Answer 10

HLA-B27

Question 11

why are HLA class I molecules not destroyed by cytotoxic t cells?

Answer 11

because CD8+ T cells only see antigens in association with class I MHC, so in the absence of an antigenic peptide. CD8+ T cell does not recognize and hence destroy HLA class I

Question 12

For class I MHC do target cells endocytose antigens? (like in class II)

Answer 12

No (therefore target cells do not have antigens contained within a phagosome)

Question 13

Is the antigen intracellular or extracellular for class I MHC?

Answer 13

intracellular/cytoplasmic

Question 14

There are several steps leading to the expression of HLA-class I/peptide on the cell surface. Each card will go through the steps one by one. SO STEP ONE:

Answer 14

antigens-ubitquitin in cytosol degraded by proteasome

Question 15

STEP TWO:

Answer 15

peptide fragments bind TAP-1 and TAP-2

Question 16

STEP THREE

Answer 16

Peptide fragments transported to the endoplasmic reticulum

Question 17

STEP FOUR:

Answer 17

Peptide bind to co-assembled HLA-1/B2 microglobulin complex

Question 18

STEP FIVE:

Answer 18

Golgi vesicles containing complexes transported to the cell surface

Question 19

STEP SIX:

Answer 19

Complexes are released from the golgi and fuse with cell membrane

Question 20

STEP SEVEN:

Answer 20

HLA-class I/peptide is now displayed on the cell surface

Question 21

STEP EIGHT:

Answer 21

Expression of HLA class I/foreign peptide signals that the cell is infected.

Question 22

what step is affected in herpes simplex virus?

Answer 22

step 2: inhibits TAP-mediated translocation of peptides from the cytosol into the ER

Question 23

what step is affected in Epstein Barr Virus?

Answer 23

step 1: inhibits activity of proteasome, therefore remains a latent infection

Question 24

what step is affected in Cytomegalovirus?

Answer 24

step 5: encodes proteins that redirect newly synthesized class I MHC molecules from the ER back into the cytoplasm for proteasome

Question 25

what does cross presentation mean?

Answer 25

exogenous antigens normally processed in phagolysosomes and presented on the cell surface with MHC class II, are now presented by MHC class I

Question 26

in what cells does cross presentation mostly occur?

Answer 26

dendritic cells

Question 27

what is cross priming?

Answer 27

CD8+ T cells are now referred to as cross priming

Question 28

so what is the consequence of cross presentation?

Answer 28

viral and non viral infection