53-MHC and Antigen Presentation

Question 1

T cells

Answer 1

effector cells of adaptive immune response, 3 types

Question 2

CD8 t cell

Answer 2

t killer cells

recognize infected cells and kill them

Question 3

CD4 t cell

Answer 3

t helper cells

regulate function of other cells and release cytokines

Question 4

gamma delta t cell

Answer 4

like innate cells, mucosal immunity

Question 5

activation of T cell

Answer 5

requires 3 signals
activation
survival
differentiation

Question 6

signal 1 for t cell

Answer 6

activation
from TCR
activation of TCR by antigen/MHC

Question 7

signal 2 for t cell

Answer 7

survival
from costimulatory receptors of antigen presenting cells
CD28 binding to B7.1 and B7.2

Question 8

signal 3 for t cell

Answer 8

differentiation

from cytokines produced by antigen presenting cells

Question 9

antigens

Answer 9

proteins or large polysaccarides that are recognized by T cells using TCR

Question 10

epitopes

Answer 10

small portion of antigens recognized by TCR

Question 11

TCR/MHC interactions

Answer 11

required for T cell activation, need 10-20 interactions, naïve cells need more

Question 12

where are MHC class 1 found

Answer 12

nucleated cells

NOT RBC or platelets

Question 13

MHC class 1 activate what

Answer 13

CD8 t killer to eliminate pathogens

Question 14

where are MHC class 2

Answer 14

antigen presenting cells
macrophages
B cells
dendritic cells

Question 15

MHC class 2 activate what

Answer 15

CD4 t helper to control adaptive immune response

Question 16

MHC class 1 peptides

Answer 16

intracellular (mostly cytosolic proteins, some ER)

dendritic make extracellular

Question 17

MHC class 2 peptides

Answer 17

extracellular

dendritic make intracellular

Question 18

MHC class 1 structure

Answer 18

2 subunits
alpha-binding
beta 2 microglobulin-stabilize
bind short amino acids 8-10

Question 19

anchor residues

Answer 19

amino acids on end that bind to MHC

Question 20

loading MHC class 1

Answer 20

• chaperone calnexin facilitates forming MHC/b2microglobulin
• transfer to chaperone calreticulin/ERp57/tapasin that interacts with TAP
• peptides produced in cytoplasm and transferred to ER with TAP complex
• peptides cleaved to 8-10 using ERAAP protease and loaded onto MHC class 1
• released after high affinity peptide is loaded

Question 21

viruses inhibiting MHC class 1

Answer 21

encode for protein to inhibit MHC class 1
evade CD8 T killer

Question 22

combat viral suppression of MHC class 1

Answer 22

NK cells recognize cells with low MHC class 1 and kill them
(presence of receptors on NK that recognize MHC class 1 and suppress NK function)

Question 23

loading MHC class 2

Answer 23

extracellular- pathogens loaded by phagocytosis, non specific antigens loaded by macropinocytosis
intracellular-loaded by autophagy

Question 24

MHC class 2 structure

Answer 24

2 proteins: alpha and beta which make peptide binding cleft

bind loner peptides, 12-20 amino acids

Question 25

MHC class 2 binding peptides

Answer 25

MHC class 2 made in ER and binds invariant chain then transported to endosome
Activation of antigen presenting cell acidifies endosome degrading invariant chain and proteins
peptides loaded onto MHC class 2 by HLA-DM

Question 26

pathogen superantigens

Answer 26

bind TCR and MHC
from bacteria, virus, mycoplasmas
cause atypical activation of t cells and cytokines
create systemic toxicity and immune suppression needed for microbial pathogenicity

Septic Shock

Question 27

CD4 T cell activation

Answer 27

different function depending on antigen presenting cell
dendritic-activate naive t cell
macrophage-cell mediated immunity
b cell-humoral immunity

Question 28

Dendritic cell activating CD4

Answer 28

activate naive T cell for clonal expansion and differentiation into effector T cell

Question 29

Macrophage activating Cd4

Answer 29

macrophage activation, activation of effector CD4 T cells at infection and inflammation
cell mediated immunity

Question 30

B cell activating CD4

Answer 30

b cell activation and antibody production, humoral immunity

Question 31

cross presentation

Answer 31

dendritic cells present extracellular on class 1 and intracellular on class 2
critical for activation of naive CD8 T cells

Question 32

DC licensing

Answer 32

activation of dendritic cells by CD4 T cells

Question 33

MHC locus

Answer 33

contains 200 genes
most gene rich regions in genome
on chromosome 6
involved in antigen presentation and peptide loading

Question 34

MHC class 1 genes

Answer 34

HLA A, B, C

Question 35

MHC class 2 genes

Answer 35

DR, DQ, DP

Question 36

polymorphism

Answer 36

multiple alleles for same gene
MHC are most polymorphic genes in humans
Class 1 higher number of alleles than Class 2

Question 37

polygeny

Answer 37

having multiple genes with same function

Question 38

function of polymorphism and polygeny

Answer 38

increase potential number of peptides that can be bound by MHC

Question 39

MHC haplotype

Answer 39

combination of MHC genes on single chromosome
inherited as a single gene
new MHC alleles and haplotype arise from point mutations

Question 40

Major diversity in MHC is where

Answer 40

peptide binding groove/cleft

Question 41

function of diversity in MHC peptide binding groove

Answer 41

each allele can bind peptide with different anchor residue

increase total pool of peptides that can be bound

Question 42

autoimmune disorders

Answer 42

linked to specific haplotypes of MHC Class 2

Question 43

presence of pathogenic haplotype

Answer 43

does not cause disease but increases disease susceptibility

Question 44

why does pathogenic haplotype increase disease susceptibility

Answer 44

better able to bind self antigens, induce cytokine production, promote polymorphisms that increase MHC or protein expression