L2 - MHC Flashcards
What does MHC do?
Binds peptides and displays them to T cells
What needs to happen to antigens for T cells to recognise them?
Be broken into peptides and displayed in association with MHC
What cells display MHC class I?
All nucleated cells in the body
What cells display MHC class II?
Antigen presenting cells (macrophages, dendritic cells, B cells)
What T cell co-receptor binds MHC class I?
CD8
What T cell co-receptor binds MHC class II?
CD4
What is the role of MHC class I? What cell does it present peptides to?
Shows peptides made within the cell to Tc cells; lets them know if the cell is infected
What is the role of MHC class II? What cell does it present peptides to?
Shows peptides from outside the cell to Th cells; alerts them to extracellular invaders
What types of peptides can MHC class I bind?
Where are the anchoring residues situated?
Short peptides (8-10 AAs)
Anchored at ends
What types of peptides can MHC class II bind?
Where are the anchoring residues situated?
Longer peptides (13-22 AAs)
Anchored at the base of the groove, peptide is free to overhang at the ends
What segments are MHC class I genes separated into?
Human leukocyte associate (HLA) A, B, and C
What segments are MHC class II genes separated into?
DP, DQ, and DR
What is the inheritance pattern of MHC genes?
They are inherited co-dominantly; both from each parent are used
What makes MHC similar to an ID card?
There are lots of different alleles and allele combinations in the population, and a person can have any combination of haplotypes
What pathway does MHC class I use to load and present peptides?
Endogenous pathway
What pathway does MHC class II use to load and present peptides?
Exogenous pathway
What types of protein are loaded into MHC class I in the endogenous pathway?
Damaged or incorrectly translated proteins
What are the stages of the endogenous pathway of MHC peptide presentation (4)?
- Proteins are broken down by proteasome
- Tap1 and 2 transporters take to ER
- Bind to MHC class I groove
- Put in vesicles and sent to surface
Proteasome, Tap, bind, vesicle
What are the names of the specific transporters that take endogenous peptides to the ER in MHC class I presentation?
Tap1 and Tap2
What are the stages of the exogenous pathway of MHC peptide presentation (5)?
- Invariant chain (CLIP) binds to MHC groove in ER
- MHC enters endosome with exogenous peptide
- Endosome enzymes break apart protein
- HLA-DM protein removes CLIP
- Peptide takes its place
Invariant, endosome, enzyme, HLA-DM, peptide
What is used as a place holder in the exogenous pathway of MHC peptide presentation?
Invariant chain (CLIP)
What removes the invariant chain in the exogenous pathway of MHC peptide presentation?
HLA-DM
