Antigen Capture and Presentation

Question 1

MHC polymorphism

Answer 1

More than 150 separate alleles have been identified within MHC gene
Many alternative versions of each MHC gene

Question 2

Co-dominant MHC expression

Answer 2

Haplotypes from both mom and dad are expressed simultaneously, creating more diversity

Question 3

Structure of MHC class I

Answer 3

a-chain encoded by MHC locus, forms 3/4 globular domains (a1, a2, a3)
B2 microglobulin- non-MHC encoded. Forms fourth domain

Question 4

MHC one binds peptides how long

Answer 4

About 8-10AAs in length

Question 5

Synthesis/expression of peptide-MHC I complexes

Answer 5

Synthesized on the ER as a-chain glycoprotein, interacts with B2 microglobulin to form MHC I.
Protein broken down into peptides in cytosol are transported by TAP into the ER and loaded on to the MHC I
Then transported to Golgi and out to membrane

Question 6

MHC II structure- binds peptides of what length

Answer 6

Two alpha and two beta chains- binds 13-18AAs long
MHC class II has greater range of peptides that it can bind to than MHC I

Question 7

CD8 binds what part of MHC I

Answer 7

a3 domain

Question 8

CD4 binds what part of MHC II

Answer 8

B2 domain

Question 9

Antigens entering peripherally are filtered by the ______ while antigens in the blood are filtered by

Answer 9

Periphery- lymph nodes

Blood- spleen

Question 10

Major cytokines produced by classical dendritic cells

Answer 10

TNF, IL-6, IL-12, IL-23

Question 11

Function/major cytokines produced by plasmacytoid DCs

Answer 11

Antiviral innate immunity and induction of T cell responses against viruses
Type I interferons

Question 12

Activated DCs- what happens

Answer 12

Lose adhesive markers and upregulate CCR7
Increase expression of MHC and CD80
Travel to secondary lymphoid tissue
Present Ag to T cells

Question 13

Presenting Ag on Class II MHC

Answer 13

Protein Ag is endocytosed and processed
Class II MHC synthesized in ER
Ii occupies the peptide binding cleft, MHC-II-Ii complex loaded into vesicle
Ii degraded to CLIP by lysosomal enzymes, HLA-DM facilitates exchange of CLIP for peptide Ag (in late endosome/lysosome)
Unbound MHCs are not displayed

Question 14

Ankylosing spondylitis

Answer 14

Inflammation of the spine
Over 88% express the HLA-B27 allele
Possible that HLA-B27 cannot bind a critical antigenic peptide/present that peptide against the agent causing the disease

Question 15

Rheumatic fever

Answer 15

Sequelae of streptococcus pyogenes infection
Generation of Abs against stept. cross react with cardiac tissue
More prone to develop this if you have HLA-DR4 allele

Question 16

Bare lymphocytes syndrome

Answer 16

First cause-TAP protein is non-functional, peptides cannot enter ER. Class I molecules will hardly be expressed
Second cause- CIITA (class II transactivator) defective. CIITA activates HLA II genes. Causes decreased MHC II expression