Flashcards in Lecture 8 Deck (24)
How many signals do T cells need to get activated? Name them.
2. Costimulation: CD28-B7
How do dendritic cells change with PAMP binding?
↑MHC 1 AND2
↑B7 = costimulatory molecule
Change chemokine receptors to move toward lymph node for T/B cell stimulation
From phagocytosis role --> processing machine
Do APCs always express costimulatory molecules?
NO - must undergo maturation to express these
DC & macrophages ↑costim molecules after binding PAMPs, getting proinflam cytokines of CD40-CD40L
B cells must be induced by T cells via CD40-CD40L
Do all T cells require co-stimulation?
Naive - always
Memory - sometimes
Effector - no
What are plasmacytoid DCs?
Make a lot of type IFNs when activated
What are fDCs?
@ secondary lymph organs
Not - MHC restricted
Display antigen to B cells
What are CD8+ DC cells?
DC cells that can express MHC1
Which has higher precursor frequency: pathogens or non-self MHC?
Non-self MHC = higher precursor frequency
For MHC2, which chains are MHC encoded - alpha or beta?
For MHC1, which chains are MHC encoded? Alpha or beta2 microglobuin?
Alpha aka the heavy chain ONLY
What are superantigens?
Creates peptide non-specific TCR/MHC interactions
General T cell activation - cytokines aren't antigen specific = non-specific inflammation
What 5 molecules are critical for MHC1 antigen processing?
1. Chaperones = calnexin, calreticulin
2. Tapasin - holds MHC 1 near TAP
3. TAP brings in peptides
4. Proteosome - unique to MHC1!
5. ERAAP - customizes peptides for the specific MHC
Describe the proteosome used for MHC1 peptide presentation.
Alpha & beta subunits = proteolytic
C term creates peptides that are more likely to bind MHC 1 molecules
Fxn upregulated by IFN gamma
- + PA28 cap to speed up peptide production
What is the source of protein antigens for MHC 1 vs 2?
1: Sometime phagosomes but usually proteins in the cytosol
2: Endosomal/lysosomal proteins internalized from extracellular environment
What is cross priming?
The ability of APCs to present on MHC1s
B/C NEED COSTIM
What is alloreactivity?
Reaction to non-self MHC
Think of transplant
MHCa + MHCa - identical match vs small DNA differences due to polymorphisms
Which viruses block peptide entry into the ER to evade immune response?
Herpes simplex 1
Which viruses retain MHC1 in the ER to evade immune response?
Murine " "
Which viruses degrade MHC 1 to evade immune response?
Murine gamma herpes
What virus binds MHC 1 at cell surface to evade immune response?
How can you increase avidity?
Tetramer of MHC-peptide with TCR
Why would you have a MHC2 deficiency? What is the net effect?
NO CD4 cells
Why would you have a MHC1 deficiency? What is the net effect?
Beta2 microglobulin mutation
NO CD8 cells