Flashcards in L7 Deck (14)
What does the T cell receptor recognize in its binding? Why is that important?
Need BOTH the correct MHC class AND peptide with epitope for TCR
How do MHC 1 and 2 differ in their basic protein structure?
- alpha 1, alpha 2, alpha 3, beta2 microglobulin
- binds short peptides - closed into groove by internal H or ionic bonds
- alpha 1 + alpha 2 & beta 1 + beta 2
- alpha/beta2 parts = transmembrane
- longer peptides, ends can stick out
What proteins form the groove for MHC1? Where is the variability found?
Alpha 1 & 2 = groove where peptide lies
- Variability in alpha helices or beta pleated sheet that makes the floor of the groove
Alpha 3 = constant region where CD8 binds
What proteins form the groove for MHC2? Where is the variability found?
Alpha 1 & beta 1
Beta 2 = where CD4 attaches
Variability = BETA 1
If you were immunized with a live virus that could replicate within your cells, which MHC would most likely present the viral peptides?
B cells would most likely express what types of MHC on their cell surface? What about skin cells?
B cells - MHC 2 (b/c APC)
Skin cell - MHC 1
What does beta2 microglobulin bind? What does does it interact with?
MHC 1 - alpha 3
What type of peptides bind MHC1?
Right anchoring resides at positions 2, 5, 8/9
How are peptides processed for MHC1 presentation?
Breakdown in proteosome
Peptide products transported by TAP --> ER
Tapasin holds MHC next to TAP so the peptide can be loaded
MHC+peptide together --> golgi --> vesicles --> membrane
What happens if MHC1 presenting cells are treated with IFN gamma?
Proteosomes become better at making peptides that will fit into MHC molecules
Boosting likelihood of getting peptides that will work in the groove
Explain peptide processing for MHC2.
Uptake of extracell via phagocytosis
Lysosome into peptides
Invariant chain sticks into middle of MHC2 for transport stability --> temporary clip inside groove
Vesicles with peptides & MHC2 fuse --> invariant chain cleaved
HLA-DM has higher affinity for temporary clip --> now any peptides in phagosome can bind the empty MHC2 groove
Where is MHC loading in 1 vs 2?
2: Vesicles moving toward membrane
What are class 1 HLA gene products? Class 2? Class 3?
Class 1 = HLA A, B, C
Class 2 = HLA DQ, DP, DM & TAP, taposin
Class 3 = complement