Test 3

Question 1

CD4+ T cell

Answer 1

helper t cell. recognizes MHC II. activated by extracellular pathogens. homodimer

Question 2

CD8+ T cell

Answer 2

cytotoxic T cell. recognizes MHC I. activated by intracellular pathogens. heterodimer

Question 3

MHC I

Answer 3

Found on all nucleated cells. Tightly binds peptide (about 9 aa). Presents endogenous peptides. Made up of alpha 1 and 2 which make up the binding region and alpha 3 which connects to the membrane and beta2 microglobulin

Question 4

MHC II

Answer 4

Found on all antigen presenting cells. Does not tightly bind peptide. Present exogenous peptides. Made up of alpha 1 and beta 1 (the binding region) and alpha 2 and beta 2 (the connecting to membrane region)

Question 5

MHC III

Answer 5

Not like I and II. molecules include several secreted proteins with immune functions: components of the complement system (such as C2, C4, and B factor), cytokines (such as TNF-α, LTA, and LTB), and heat shock proteins. New classification classifies cytokines (such as TNF-α, LTA, and LTB), AIF1 and heat shock proteins as Class IV MHC Genes (found at telomeric end of MHCIII)
MHCIII have NO structural similarities to MHC I or II

Question 6

What can T cell receptors recognize?

Answer 6

T cell receptors (TCR) recognize antigen as peptides in the context of (self) MHC I or II molecules. TCRs cannot recognize soluble antigens

Question 7

exogenous antigen

Answer 7

aka Extracellular pathogen, intravesicular pathogens, toxins. Can replicate outside the cell, usually taken in by phagocytosis. think bacteria

Question 8

endogenous antigen

Answer 8

aka Intracellular pathogen, cytosolic pathogen, virus. Only replicates inside the cell. think virus and v specific bacteria

Question 9

Why are CD4 and CD8 considered co-receptors

Answer 9

They facilitate the connection between the TCR of the T Cell and the MHC of the Antigen Presenting Cell

Question 10

degenerate or promiscuous binding specificity

Answer 10

MHC recognizes aspects of the peptide are common to all peptides – The ends of the peptide and the peptide backbone

Question 11

defective ribosomal products (DRiPs)

Answer 11

misfolded proteins that are recognized and tagged by ubiquitin for rapid degradation by the proteasome

Question 12

constitutive proteasome vs immunoproteasome

Answer 12

Constitutive proteasome
Degrade defective or old proteins. Expressed in healthy, normal tissues and in immune-privileged organs such as the brain.
Immunoproteasomes
Expressed in cells stimulated by gamma interferon (IFN-γ) or tumor necrosis factor alpha (TNF-α), and in primary and secondary lymphoid organs.

Question 13

TAP 1/2

Answer 13

transporter associated with antigen processing. The peptides generated by the proteasome are transported into the ER by TAP

Question 14

Peptide loading complex

Answer 14

Calreticulin, ERp57, and PDI

Question 15

Are empty MHC stable compounds?

Answer 15

no

Question 16

ERAP

Answer 16

cuts down peptides that bind to MHC I that are too long

Question 17

Steps in MHC I peptide loading

Answer 17

1) Presence of Cytosolic Antigen 2) Generation of peptides by antigen degradation 3) Shuttling of peptides into ER 4) Peptide loading 5) Transport of peptide MHC I to surface